10th class physics Chapter 1 Important Long Questions Prepare Online

Question: 1

Q (5) Define simple harmonic motion prove that vibrating motion of mass attached to a spring is SHM? A simple pendulum complete one vibrating in 2 seconds calculate its length when g =10 ms-2?

Answer: 1

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Part (A) Simple harmonic motion: Definition: Simple harmonic motion is occurs when the net force is proportional to the displacement from mean position and is always directed is towards mean position. Motion of mass attached to spring one of simplest motion is horizontal mass spring system as shown in figure.If the spring is compressed specked though the small displacement from x its mean position it exerts a force i on mass. By hooks law:e The force is directly proportional to the change in length x of spring [f=- kx] when x is displacement of mass from mean position k is spring constant. Spring constant: k = f (nm-1) x It is the ratio of force to change in length. It i measure of stiffness of spring. Stiff spring have larger k and soft spring have smaller k. Restoring force: A restoring force always pushes or pulls the scathing body toward the mean position. fr = - f So, fr = - kx from newton's and law of motion fr = ma putting value of fr in er (i) ma = - kx A = - k x m a k/m = constant a = - constant x a*-x Direction of Acceleration: Initially the mass m is at rest, so resultant force on the mass is zero, when the mass moves from O_____A the restoring force is increases, but when mass come back A____O its restoring force decreases and velocity becomes maximum due to inertia mass do not stop on O, but moves O_____ B and in doing so the restoring force increases and velocity decreases and again from O______ B , the restoring force decreases again and finally spring comes back to mean position. Time period ______ t = 2k , m/k Part (B) Given data: Time period of simple pendulum =t= 2 sec. acceleration due to gravity = g= 10ms -1 To find: length of pendulum = L =? Formula:

Question: 2

Q (6) (a) Distinguish between longitudinal and transverse waves with suitable example? (b) A ripple tank whose width 80 cm, across at one end vibrator produce waves whose frequency is 5 Hz and waves length is 40 mm. Find the time the waves need cross the ripple tank?

Answer: 2

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Part (A) Longitudinal Waves: The waves in which the particle of medium move back and for the along the direction of propagation of waves. Explanation: Longitudinal waves one also called Compression waves sound. Sound waves also travel from one place to another place in form of longitudinal pattern. These waves travel in form of compression and rare fractions. Production of waves : Consider a slinky spring, attached the spring to firm support at one end and hold, the other end in your hand and start moving back and forth quickly, a series of disturbance produces in the spring in form of compression and rare fractions. Compression and rare fraction: Compression are those region where the particle of medium are closed together while rare fraction are those region where the particle medium are spaced a part. Part (B) Transverse Waves: In case of transverse waves the motion of particle of medium is perpendicular to direction of wave. Production of Wave: There wave can be produced with the help of slinky spring.Speech out the slinky spring along the smooth floor with one end fixed, grasp one end and move up and down. Crest and troughs will b formed Crest and Troughs: Crest is part of waves above the mean position.Trough is part of wave below the mean position. Part (B) Given data: lenghth =1= 8am =0.08m frequency = 7 = 5Hz wave length = 40 mm = 4*10-3m To find: time taken =t=? Solution: as we know that v=f v = (5) (0.04) = 0.2 m/s and v = d/t t = d/v t = 0.08/0.02 t = 4s

Question: 3

<div>Q (6)</div><div>(A) What do you know understand by the longitudinal wave? Describe the</div><div>Longitudinal nature of sound waves?</div><div>(B)A normal conservation invloves sound intensities of about 3.0*10-6</div><div>Wm-2.What is the decibel level for this intensity?</div><div><br></div><div><br></div><div><br></div>

Answer: 3

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Part (A)

Reflecion of sound:

When sound is incident on the surface of a medium it bounces back into the first medium .This phenomena is called echo or reflection of sound.

Example:

When we clap or shout near a reflection surface such as tall building or a mountain, we hear the

Same sound again a little later.This sound which we hear is called an echo and is a result of reflection of sound from the surface.

Explanation:

The sensation of sound persists in our brain for about 0.1s.To hear a clear echo the time internal between our sound and the reflected sound must be atleast 0.1s.If we consider speed of sound to be 340ms-1 at a normal temperature in air we will hear the echo after 0.1s. The total distance covered by the sound from the point of generation, to the reflecting surface and back should be at least 340*0.1 340m. Thus for hearing distinct echoes , the minimum distance of the obstacle from the source of sound must be half of this distance, that is 17m.Echoes may be heard more than once due to successive or multiple reflection.

Part (B)

Given data:

Frequency (f) =512Hz

Speed of sound (v)= 140ms-1

Wavelength of sound (λ)=?

Solution

We know that; v = f λ

v/f = λ

λ =v/f

putting given values :

λ = 140/512

λ = 0.273m

Question: 4

Q (6)<div><div><br></div><div>(A) What do you know understand by the longitudinal wave? Describe the</div><div>Longitudinal nature of sound waves?</div><div>(B) A normal conservation invloves sound intensities of about 3.0*10-6</div><div>Wm-2.What is the decibel level for this intensity?</div></div>

Answer: 4

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Part (A)

Longitudinal Waves:

The longitudinal waves the particles of the medium vibrate Paralled to the direction of propogation of wave e.g sound wave.

Nature of sound:

Sound waves are compressional in nature which can explained by following experiment when we strike the tuning fork on rubber , pad its prongs with begin to move between position AOB When prongs move from O to B , The exert pressure on the adjacent layer of air and compression is produced. The compressed layer of air is compress the layer of air next t it and so when prongs move from B to A , the pressure on layer of air is decreased and rare faction is produced. This rare faction is transferred to the air layer next to it and so on. So when the tuning fork moves back and forth rapidly, a series of compression and rare faction is produced due t which sound waves propagate through air. As the direction of sound wave is along the direction of oscillating air molecules, it shows that sound wave is compressional in nature.

Y /AOB= IIIIIIIIIIIIIIIII vibrate of tuning fork

Y/OB = IIIIIIIIIIIIIIIII after striking with a rubber hammer

Y/AD = IIIIIIIIIIIIIIII

Wavelength:

Distance between two consecutive compressions or rare faction is the wave length of sound waves it is donated by λ.

Part (B)

Given data:

Intensities of sound = I=3*10-6Wm-2

Threshold intensity = Io =10-12 Wm-2

Solution:

We know that:

L-Lo= Lo I/I db

= 10 log(3*10-6)db

(10-12)

= 10 log (3*10-6 *10-12)db

= 10 log (3*10/6)db

= 10 (log 3+ log 10/6)db

= 10 (0.477+6 log/10)db

= 10 ( 0.477 +6) db

= 10 *6.477

= 64.77 db

L-Lo= 64.8 db

Question: 5

<p class="MsoNormal">What is electromagnetic wave?</p>

Answer: 5

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This wave which do not require medium for their propagation are called electromagnetic waves example: X rays light waves heat waves

Question: 6

<p class="MsoNormal">Define hooks law for mass spring system what I usefulness of spring system (constant)?</p>

Answer: 6

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This law state that the force needed to compress or streched the spring by some distance is directly proportional to the distance: f*-x _____ f= kx

The force is basically restoring force where k is spring constant which is measure of stiffness of spring so it tell us the nature of spring.

Question: 7

<p class="MsoNormal">Define wave length?</p>

Answer: 7

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The distance between the two consective crest or through is called wavelength it is represented by greek symbol lamda.

Question: 8

<p class="MsoNormal">Discuss wave motion?</p>

Answer: 8

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Wave motion is basically the propagation of disturbances produced by the source in equal intervals time during wave motion waves transport energy from one point to other e.g energy transported by water waves.

Question: 9

<p class="MsoNormal">Define Compression?</p>

Answer: 9

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A compression is region in longitudinal wave where the particles of medium are closest together.

Compressed spring portion producing compression.

Question: 10

<p class="MsoNormal">What is simple pendulum?</p>

Answer: 10

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A simple pendulum is simple harmonic oscillator that has small massed bob suspended from light string of length m .

Time period is given by: t = π l/g

Question: 11

<p class="MsoNormal">Difference between vibration and amplitude?</p>

Answer: 11

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One complete round trip of vibrating body about its mean position is caused one vibration.

The maximum displacement of vibrating body on each side from mean position .

Question: 12

<p class="MsoNormal">Define Vibration frequency amplitude?</p>

Answer: 12

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Vibration: One complete round trip of vibrating about its mean position is called one vibration.

Frequency: The number of vibration or cydes of a vibrating body in one second is called frequency it Is reciprocal of time period f = 1/1

Amplitude: The maximum displacement of vibrating body on either side from its mean position is caused its amplitude.

Question: 13

<p class="MsoNormal">Define ripple tank?</p>

Answer: 13

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Ripple tank is a device used to produce water waves and to demonstrate different properties of water waves like reflection refraction and diffraction.

Question: 14

<p class="MsoNormal">Define simple harmonic motion what are necessary condition for body to execute simple harmonic motion?</p>

Answer: 14

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When an object oscillates about fixed position such that its acceleration is directly proportional to its displacement from mean position and always directed toward mean position its motion is caused is SHM

A & -x

There must be elastic restoring force acting on system the acceleration of system should be directly proportional to displacement and always directed toward mean position.

Question: 15

<p class="MsoNormal">Define diffraction?</p>

Answer: 15

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The bending or spreading of wave around sharp edges or corner of obstacles or slits is called

diffraction.

Question: 16

<p class="MsoNormal">Define wave length what are it types their example?</p>

Answer: 16

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The wave is disturbance in the medium which causes the particle of medium the undergo vibratory motion about their mean position is equal intervals of time.

Types:

Mechanical waves:

The waves which require any medium for their propagation are called mechanical waves e.g

Water waves , sound waves

Electromagnetic waves:

The waves which require any medium for their propagation are called mechanical waves e.g

Water waves ,sound waves

Question: 17

<p class="MsoNormal">Define reflection?</p>

Answer: 17

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The wave moving in one direction in medium and fall on the surface of other medium they bounce back into the first medium such that the angle of incidence to the angle of reflection.

< i= <r

Question: 18

<p class="MsoNormal">Define mechanical waves explain different types with suitable example?</p>

Answer: 18

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The waves which require the medium for their propagation are called mechanical waves .

Types:

Longitudinal waves:

In longitudinal waves the particle of medium move back and forth along the direction of waves e.g

Waves produced in slinky spring by to and for motion.

Transverse waves:

In transverse waves the vibratory motion of particles of medium is perpendicular to the direction of propagation of waves e.g waves on surface of water.

Question: 19

<p class="MsoNormal">If the length of simple pendulum is doubled what will be change in its period?</p>

Answer: 19

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The time period of simple pendulum given by: t = 2 π l/g

If length is doubled l= 2l

T = 2 π 2l/g

T = 2 π (2) l/g

T = (2) 2 π l/g

T = 1.44 2 π l/g

Hence the time period increases 1.44 times.

Question: 20

<p class="MsoNormal">Difference between longitudinal and transverse waves?</p>

Answer: 20

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The waves in which the particle of medium move back and forth along the direction of propagation of waves the wave has compression and rare fraction e.g the wave produced in slinky spring sound waves

Transverse waves:

The waves in which the vibratory motion of particles of medium is perpendicular to the direction of propagation of wave.e.g water waves and light waves.

Plane waves in ripple tank under go refraction when they move from deep to shallow water what

Question: 21

<span style="font-size:11.0pt;line-height:115%; font-family:"Calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family: Calibri;mso-fareast-theme-font:minor-latin;mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman";mso-bidi-theme-font:minor-bidi; mso-ansi-language:EN-US;mso-fareast-language:EN-US;mso-bidi-language:AR-SA">changes occurs in speed of sound?</span>

Answer: 21

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In ripple tank the frequency of wave is constant and directly varies with frequency of vibrator but frequency of wave is constant and speed varies and wave length when the water wave enters the shallow region from deep region wave length decreases so apeed also decreases.

Question: 22

<p class="MsoNormal">Define crest and trough?</p>

Answer: 22

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Crest: The part of wave above the mean position is called crest.

Question: 23

<p class="MsoNormal">Define time period?</p>

Answer: 23

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The time taken by vibrating body to complete one vibration is called time period

T = I/f

Question: 24

<p class="MsoNormal">What is meant by wave equation? Describe the relation for wave equation i.e v=f r?</p>

Answer: 24

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The equation which explains the motion of the waves in terms of its speed is known as wave equation

The speed of wave given by :

V = distance/time = s/t

As s Is the distance = wavelength

Time interval t = I = time period, so

V = i/t

As f = i/i

So, v =fr

Question: 25

<p class="MsoNormal">What do you mean by reflection of sound?</p>

Answer: 25

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When the sound travel in given medium its strikes the surface of another medium and bounce back in some direction this phenomena is called reflection of sound this process is also known as echo.

Question: 26

<p class="MsoNormal">Define reflection of waves?</p>

Answer: 26

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When the waves moving in one medium fall on the surface of another medium they bounce back into the first medium such that angle of incidence <I should equal t angle of reflection <r

<i=<r

Question: 27

<p class="MsoNormal">What types of waves do not require any material medium for their propagation?</p>

Answer: 27

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The waves which do not require any material medium for their propagation are caused electromagnetic waves e.g xrays, light ways.

Question: 28

<p class="MsoNormal"><span style="font-size: 10.5pt; line-height: 107%; font-family: Arial, sans-serif;">what is simple Harmonic (SHM)? What are the conditions for an object to oscillate with SHM?</span><o:p></o:p></p>

Answer: 28

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Vibration or oscillation is repeated back and forth motion along the same path. Vibrations occur in the vicinity of a point of stable equilibrium. An equilibrium points is a point at which the net force acting on the body is zero . An equilibrium point is also called stable point when at small displacements from it the net force pushes the body back to the equilibrium point. Such a force is called a restoring force since it tends to restore equilibrium. Consider a bowl and ball example under stable equilibrium condition. When ball is displaced from its equilibrium position, it will start moving under restoring force towards equilibrium position, opposite to the displacement `x' . After reaching equilibrium position the object will continue under inertia and will reach the other extreme position and thus it will continue to oscillate back and forth. Simple Harmonic motion

Question: 29

show that the mass spring system executes Simple Harmonic Motion (SHM)?

Answer: 29

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Consider a block of mass m attached to one end of elastic spring, which can move freely on a frictionless horizontal surface. When the block is displaced the elastic restoring force pulls the block towards equilibrium position. For an ideal spring that obeys Hook's Law the elastic restoring force F_res is directly proportional to the displacement x from equilibrium position.

F_res α-x

Since F and x always have opposite directions therefore we have a negative sign in equation. Each spring is different , and so is the force required to deform it.

The stiffness of the spring, or spring constant, is represented by the letter k. The equation for Hooke's law is

F_res= -kx

Thus motion of mass attached to spring is SHM. Restoring force produces acceleration in the body, given by newton's second law of motion as

F_res = ma

Comparing F_res =-kx and F_res= ma we get

ma = -kx

or a=k/m x

As spring constant k and mass m does not change during oscillation of mass attached to spring therefore they are regarded as constants

a α -x

If the restoring force obeys Hooks law precisely, the oscillatory motion of mass attached to sping is simple harmonic

Question: 30

show that the mass spring system executes Simple Harmonic Motion (SHM)?

Answer: 30

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Consider a block of mass m attached to one end of elastic spring, which can move freely on a frictionless horizontal surface. When the block is displaced the elastic restoring force pulls the block towards equilibrium position. For an ideal spring that obeys Hook's Law the elastic restoring force F_res is directly proportional to the displacement x from equilibrium position.

F_res α-x

Since F and x always have opposite directions therefore we have a negative sign in equation. Each spring is different , and so is the force required to deform it.

The stiffness of the spring, or spring constant, is represented by the letter k. The equation for Hooke's law is

F_res= -kx

Thus motion of mass attached to spring is SHM. Restoring force produces acceleration in the body, given by newton's second law of motion as

F_res = ma

Comparing F_res =-kx and F_res= ma we get

ma = -kx

or a=k/m x

As spring constant k and mass m does not change during oscillation of mass attached to spring therefore they are regarded as constants

a α -x

If the restoring force obeys Hooks law precisely, the oscillatory motion of mass attached to sping is simple harmonic

Question: 31

What is simple pendulum? The forces acting on the simple pendulum. Aslo show that simple pendulum executes simple harmonic motion

Answer: 31

31-47

Simple pendulum is an idealized model consisting of a point mass suspended by a weightless, in - extendable string supported from a fixed frictionless support. A simple pendulum is driven by the force of gravity due to the weight so suspended mass`m' (W=mg). A real pendulum approximates a simple pendulum if

the bob is small compared with the length l,

mass of the string is much is much less than the bob,s mass, and

the cord or string remains straight and doesn't stretch.

Pull the pendulum bob aside and let it go; the pendulum then swings back and forth. Neglecting air drag and friction at the pendulum's pivot, these oscillations are periodic We shall show that, provided the angle is small, the motion is that of a simple harmonic oscillator.

▲QRS we resolve the weight (W=mg) in to two components `mg sin0' and mgcos0'.

The components `mg cos0' is balanced by the Tension `T' in the string. The restoring force is only provided by component `mg sin0' Therefore

F_rest = -mgsin0 eq (1)

Also note in the figure that only for small angles the arc length `s' is nearly the same length as displacement `x'

Therefore form ▲OPQ sin0= x/l eq (2)

Putting eq 2 in eq 1

F_rest = -mgx/l eq 3

Since mass `m', acceleration due to gravity `g' and length `l' are constant for simple pendulum can be approximated as is simple harmonic motion.

Also by Newton's second law of motion F_rest = ma eq (4)

camparing equation 3 and eq 4 ma= -mgx/l

or a = - g/l x

since g and l are constants for oscillating simple pendulum, therefore

a α-x

Hence , when released the mass will move towards the equilibrium position , will cross over it due to inertia and will execute Simple Harmonic Motion (SHM)

Question: 32

What is wave motion? How waves can be categorized?

Answer: 32

32-47

Wave motion is related fto oscillation, when the energy moves through the wave the particles of the medium executes simple harmonic motion about their equilibrium position. For example, take a rope and color a part of it. Attach one end of the rope to the wall and wiggle the other end regularly and continuously. The number of waves will be produced forming a wave train, Observer the color marking, it will execute oscillations about certain mean position,

When a stone is dropped in a pond water, ripples (waves) are seen on the surface of water, the particles of water that that absorb energy and start oscillating from the impact of the stone. These particles transfer some of its energy to the neighboring particles which also start vibrating, In this way gradually other particles on the water surface also start oscillating and energy is spread out throughout the water pond.

Question: 33

prove the relation between wave speed , wavelength and frequency of wave?

Answer: 33

33-47

Wave speed

The distance traveled by wave in unit time is called wave speed

v = distance/time =▲s/▲t eq (1)

The distance traveled by wave equal to one wavelength `π' (▲s=π) is covered in time equal to time period T (▲t = T), therefore equation 1 can be written as

v = π/t eq (2)

Since time period `T' and frequency `f' are reciprocal of each other, therefore

f=1/T eq (3)

Putting eq 3 in eq 2 we get

v=fπ

so it is also called universal wave equation as it applies to all waves and gives the waves speed in terms of frequency f and wavelength π.

Question: 34

Using ripple tank explain reflection, refraction and diffraction of waves

Answer: 34

34-47

Ripple tank is an experimental setup to study the two dimensional features or characteristics of waves mechanics such as reflection, refraction and diffraction. it consist of shallow tray of water with a transparent base, usually illuminated from above, so that light shines through the water, the ripples on the water show up as shadows (bright and dark lines) on the screen underneath the tank .

Sometimes for easy visualization, a reflector is used to project the screen on front base fo the ripple tank . Straight waves can be set up by using a straight dipper, while circular waves can be formed by using a spherical dipper. Both dipper are vibrated up and down by an electric motor.

For a two or three dimensional wave such as a water wave, we are concerne with wave fronts , by which we mean all the points along the wave forming the wave crest (What we usually refer to simply as a "wave "at the seashore). A line drawn in the direction of wave motion, perpendivular to the wave front, is called a ray,

Question: 35

Prove that the motion of a mass attached to a spring is SHM?

Answer: 35

35-47

Simple Harmonic Motion: simple harmonic motion occurs when the net force is directly proportional to the displacement from the mean position and is always directed toward the mean position.

Motion of mass attached to a spring: one of the simplest types of oscillatory motion is that of horizontal mass spring system.

Increase in length: if the spring is stretched or compressed through a small displacement x from its mean position , it exerts a force F on the mass. According to Hooke's law this force is directly proportional to the change in length x of the spring i.e.

F=-Kx

The negative sign means that force exerted by the spring is always directed opposite to the displacement of mas. Because the spring force always acts towards the mean position. In the following equation x is the displacement of mass from mean position O and K is a constant define as:

" the ratio between external force acting on a spring and increase in its length is known as spring constant".

K= F/x

The value of K is a measure of the stiffness of spring. Stiff spring have large K value, and soft spring have small value of K.

According to 2nd law of motion.

F=ma

ma=-Kx

a= -Kx /m

K/m= -constant * x

It means that the acceleration of a mass attached to a spring is directly proportional to its displacement from the mean position. Hence, The horizontal motion of a mass spring system is an example of simple harmonic motion.

Restoring force: a restoring force always pushes or pulls the object performing oscillatory motion towards mean position.

Mass at rest: initially the mass is at rest at mean position O and the resultant force on the mass is zero.

When mass is pulled through displacement "x" to extreme A: suppose the mass pulled through distance x up to extreme position A and then released. The restoring force exerted by spring on mass will pull it towards mean position O. Due to restoring force the mass moves back, towards the mean position O. The magnitude of the restoring force decreases with the distance from mean position and becomes zero at O. However , the mass gains speed as it moves towards the mean position and its speed become maximum at O.

Mass at extreme position B: due to inertia the mass does not stop at mean position O but continues with motion and reaches the extreme position B.

As the mass moves from mean position O to extreme position B , the restoring force acting on it towards the mean position steadily inverse in strength. hence speed of mas decrease as it moves towards the extreme position B. The mass finally comes briefly to rest at extreme position B. Ultimately the mas returns to the mean position due restoring force.

This process is repeated , and the mass continues to oscillate back and forth about mean position O. Such motion of a mass attached to a spring on a horizontal frictionless surface us SHM.

Question: 36

Discuss the K.E and P.E at different positions in a mass spring system?

Answer: 36

36-47

The K.E. and P.E at different positions in a mass spring system are given below

Initially the mass m is at rest at mean position O thus its KE and P.E both are zero
When the mass m is pulled from mean position O to extreme position A its P.E become maximum at A.
Now from position A when mass m is reached it tend to move towards mean position O. Now at mean position K.E becomes maximum and P.E becomes zero.
Due to inertia "m" does not stop at mean position "O" and continues its mean position towards extreme position B, thus when mass "m" moves from O to B its K.E decreases and P.E increases. At position B, K.E becomes zero and P.E becomes maximum.

Question: 37

Prove that the motion of a ball in a bowl is the example of SHM?

Answer: 37

37-47

Simple harmonic motion: simple harmonic motion occurs when the net force is directly proportional to the displacement fro the mean position and is always directed towards the mean position.

Ball and bowl system: the motion of a ball placed in a ball is an example of simple harmonic motion .To and fro motion of ball about mean position is simple harmonic motion.

Ball at rest: when the ball is a t the mean position O, that is , at the center of the bowl, net force acting on he ball is zero. In this position, weight of the ball acts downwards and is equal to the upward normal force of the surface of the bowl. hence , there is no motion and the ball is at rest.

By bringing the ball to extreme position: now if we brig the ball to position A and then release it, the ball will start moving towards the mean position O due to the restoring force caused by the weight . At position O the ball get maximum speed and due to inertia it moves towards extreme position B.

Ball going towards the extreme position B ; ball is going towards the position B, the speed of ball decreases due to restoring force which acts when towards mean position.

Ball at mean position B: ball at position B stops for a while and then again moves towards the mean position O under the action of the restoring force . At B position the speed of ball is zero. Ball's to and fro motion continuous about mean position O till all of energy is lost due to friction.

Question: 38

Explain that the motion of bob of a simple pendulum is an example of SHM?

Answer: 38

38-47

SHM: simple harmonic motion occurs when the net force is directly proportional to the displacement from the mean position and is always directed towards the mean position.

Simple pendulum: a simple pendulum consists of a small bob of mass "m" suspended from a light string of length "l" fixed at its upper frictionless end.

Bob at mean position: in the equilibrium the mean position O, the net force on the bob is zero and the bob is stationary.
Motion of bob from extreme position: if we bring the bob to extremes position A , the net force is not zero

There is no force acting along the string as the tension in the string cancels the components of the weight. Hence there is no motion along this direction.

The component of the weight is directed towards the mean position and acts as a restoring force due to its force the bob starts moving toward the mean position O. The restoring force still acts towards the man position O and due to this force the bob again starts moving towards the mean position O. In this way, the bob continues its to and from motion about the mean position O.

Question: 39

Write note on damped oscillation?

Answer: 39

39-47

Damped oscillations: the oscillations of a system in the presence of some resistive force are called damped oscillations.

Vibratory motion of ideal system: vibratory motion of ideal systems in the absence of any friction or resistance continues indefinitely under the action of a restoring force.

damping: practically , in all systems, the force of friction retards the motion, so the systems do no a oscillated indefinitely.

The friction reduces the mechanical energy of the system as the time passes and the motion is said to be damped . This damping progressively reduces amplitude of the vibrations.

Shock absorbers: shok absorbers in automobiles are one practical applications of damped motion. A shok absorber consists of a piston moving through a liquid such as oil. The upper part of shock absorber is firmly attached the the body of car. When the car travels over a bump on the road, the car may vibrate violently.

The shok absorber damped these vibration and convert their energy into heat energy of the oil.

Question: 40

Define waves and explain wave motion?

Answer: 40

40-47

Wave: "a wave is a disturbance in the medium which causes the particles of medium to undergo vibratory motion about their mean position in equal interval of time".Wave motion: waves play an important role in our daily life. It is because waves are carried or energy and information over large distances.Wave requires some oscillating or vibrating source . Here we demonstrate the production and propagation of different wave with the help of vibration motion of objects.

Question: 41

Write note on types of mechanical waves?

Answer: 41

41-47

Types of Mechanical waves: depending upon the direction of displacement medium with respect to the direction of the propagation of wave itself, mechanical waves may be classified as

Longitudinal waves
Transverse waves

Question: 42

Write a note on waves as carrier of energy?

Answer: 42

42-47

Waves as carriers of energy: energy can be transferred rom one place to another through waves.

Example: when we shake the stretched string up and down, we provide our muscular energy to the string. As a result, a set of wave can be seen travelling across the string. The vibrating force from the hand disturbs the particles of string and sets them in motion. These particles then transfer their energy to the adjacent particles in the string. Energy is thus transferred from one place of the medium to other .

Dependence; the amount of energy carried by the wave depends on the distance of the stretched string from its rest position. That is the energy in a wave depends on the wave amplitude of wave. If amplitude and frequency are greater that more energy will be transfer.

Example: if we shake the string faster, we give more energy per second to produce wave of higher frequency, and wave delivers more energy per second to the particles of the string as it moves forward.

Question: 43

Derive relation between velocity, frequency and wavelength.

Answer: 43

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Velocity of wave: wave is the disturbance in a medium which travels from one place to another and hence has a specific velocity of travelling , called as velocity of wave.

Which can be defined mathematically as:

Velocity= distance /time

v=d/t

if time taken by wave is moving from one point to another is equal to its time period T, then distance covered by wave will be equal to one wavelength .

Time period T is reciprocal of frequency.

T=1/f

Question: 44

Write a note on Ripple Tank?

Answer: 44

44-47

Ripple Tank: "ripple tank is a device to produce water waves and to study their characteristics".

Apparatus: this apparatus consist of a rectangular tray having glass bottom and is placed nearly half meter above the surface of a table. Waves can be produced on the surface of water present in the tray by means of vibrator(paddle).

Working of vibrator: the vibrator is an oscillating electric motor fixed on a wooden plate over the tray such that its lower surface just touches the surface of water. On setting the vibrator ON, this wooden plate starts vibrating to generate water waves consisting straight wave fronts.

Working of electric bulb: an electric bulb is hung above the tray to observe the image of water waves on the paper or screen.

Crest and Trough: the crests and troughs of the waves appear as bright and dark lines respectively , on the screen.

Question: 45

Explain reflection with the help of Ripple Tank?

Answer: 45

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Reflection of Wave: " when waves moving in one medium fall on the surface of another medium they bounce back into first medium such that angle of incidence is equal to the angle of reflection this is called reflection of waves".

Explanation; place a barrier in ripple tank. The water waves will reflect from barrier. If a barrier is placed at an angle to wave front reflected waves can be seen to obey law of reflection i.e. the angle of incident wave along the normal will be equal to angle of reflected wave.

Question: 46

Explain refraction with the help of Ripple Tank?

Answer: 46

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Refraction of wave: " when wave from one medium enters into the second medium at some angle, its direction of travel changes. This phenomenon is refraction of wave".

Question: 47

Explain diffraction with the help of Ripple Tank?

Answer: 47

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Diffraction: "the bending or spreading of wave around the sharp edges or corners of obstacles is called diffraction".

Explanation; now we observe the phenomena of diffraction of water waves. Generate straight waves in a ripple tank and place two obstacles in the line in such a way that separation between them is equal to the wavelength of water waves. After passing through a small slit between the two obstacles, the waves will spread in every direction and change into almost semicircular pattern.

Physics Chapters

10th Class Chapter 1 Physics Long Questions

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