11th Class Physics Chapter five Short Questions with Answers Solved

Question: 1

Why you wear seat belts?

Answer: 1

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During collision, the passengers move forward towards the windscreen due to inertia. The seat belt prevents the passenger from moving forward. And lessened the chances of injury.

Question: 2

Define angular velocity, How its direction is determined?

Answer: 2

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The rate of change of angular displacement is called angular velocity. The direction of angular velocity is along the axis of rotation and can be determined by right hand rule:

"Grasp the axis of rotation in right hand with the figures curling in the direction of rotation then the erect thumb will give the direction of angular velocity."

Question: 3

When mud files off the tyre of a moving bicycle, I what direction does it fly?

Answer: 3

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Adhesive force between mud and tire is weal. When the mud files off the tyre of a moving bicycle, it always files along the tangent to the tyre. Because linear velocity is always tangent to the circle.

Question: 4

Define centripetal force and centripetal acceleration.

Answer: 4

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The force needed to bend the normally straight path of the particle into a circular path is called the centripetal force.

The instantaneous acceleration of an object traveling with uniform speed in a circle is directed towards the centre of the circle and is called centripetal acceleration.

Question: 5

Explain the difference between tangential velocity and angular velocity.

Answer: 5

5-35

The linear velocity of a particle moving along a curve or circle is called tangential velocity. Its direction is always along the tangent to the circle.

The rate of change of angular displacement is called angular velocity.The direction of angular velocity is along the axis of rotation of the body by right hand rule. V= rw

Question: 6

State the right hand rule to find the direction of angular displacement.

Answer: 6

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It states that

"Grasp the axis of rotation in right hand with the fingers curling in the direction of rotation , then the erect thumb will give the direction of angular velocity and angular momentum"

Question: 7

Define angular momentum and give its dimension.

Answer: 7

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Question: 8

Define angular displacement and write its S.I unit.

Answer: 8

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Question: 9

Define angular displacement.

Answer: 9

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Question: 10

Define angular velocity give its units and dimensions.

Answer: 10

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The rate of change of angular displacement is called angular velocity. The direction of angular velocity is along the axis of rotations of the body.

S.I unit of angular velocity = rad/s

Dimensions of angular velocity = [T^-1]

Question: 11

What is meant by centripetal force?Write down its formula

Answer: 11

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Question: 12

What is mean by angular momentum?

Answer: 12

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Question: 13

State the law of conversation of angular momentum.

Answer: 13

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Question: 14

What are Artificial Satellites and how they move around the earth?

Answer: 14

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Satellites are the objects that orbit around the earth.They are put into orbit by rockets and are held in orbits by the gravitational pull of the earth.

Question: 15

Explain conservation of direction of angular momentum.

Answer: 15

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The direction of angular momentum along the axis of rotation remains fixed. This is due to the fact that the axis of rotation of an object will not change its orientation unless an external torque causes it to do so .

Question: 16

Why is the axis of rotation of Earth remains fixed in one direction with respect to the universe around it?

Answer: 16

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The major force acting on Earth is the pull of the Sun and no other sizeable toque is experienced by it. The Earth's axis of rotation, therefore remains fixed in one direction with reference to the universe around us.

Question: 17

Define Moment of Inertia.Write its formula.

Answer: 17

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The property of the body to resist any change in its state of rest or uniform angular velocity is called moment of inertia. For a point mass 'm'situated at a distance 'r' from the axis of rotation , the moment of inertia 'I' is given by ; I=mr²

Significance;

Moment of inertia plays the same role in angular motion as that of mass plays in linear motion. It is also called measure of rotational inertia in angular motion.Moment of inertia determines the angular acceleration while mass determines the linear acceleration.

Question: 18

What is meant by moment of inertia? Explain its significance.

Answer: 18

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The product of mass of the particle and square of its perpendicular distance from the axis of rotation is called the moment of inertia.

I =mr²

^{The moment of inertia plays the same role in angular motion as the mass in linear motion.}

Question: 19

An object orbiting around the earth in said to be a freely falling body. Why?

Answer: 19

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An object in orbits is said to be freely falling , because the trajectory of its fall has the same curvature as Earth's surface. In fact, the object is falling towards the center of earth but because of spherical shape of earth, it never reaches the surface of earth.

Question: 20

On what factors moment of inertia depends?

Answer: 20

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The moment of inertia is I =mr²

^{So it depends upon the mass of the body and its distance from the axis of rotation.}

Question: 21

Why banked tracks are needed for turns?

Answer: 21

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Banked tracks are needed because friction alone cannot provide energy for centripetal force.

If the road is banked, so that the outer edge is above the inner edge, then a portion of the normal force from the road on the tyre points towards the center of the track; this fraction of the normal force can provide enough centripetal force to keep the car moving in a circle.

Question: 22

How would you determine the direction of angular momentum?

Answer: 22

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The direction of angular momentum can be determined by right hand rule:

"Grasp the axis of rotation in right hand with the figures curling in the direction rotation then the erect thumb will give the direction of angular momentum."

Question: 23

State the direction of the following vectors in simple situation:

A) Angular Momentum B) Angular Velocity

Answer: 23

23-35

The direction of angular momentum and angular velocity can be determined by right hand rule;

"Grasp the axis of rotation in right hand with the figures curling in the direction of rotation, then the erect thumb will give the direction of angular velocity and angular momentum."

Question: 24

Why the microwaves are used in satellite communication?

Answer: 24

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Micro waves are used in satellite communication because they travel in a narrow beam, in a straight line and pass easily through the atmosphere of the earth.

Question: 25

What is meant by centripetal force? Write down its formula.

Answer: 25

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Question: 26

What is meant by INTEL SAT? At what frequencies the INELSAT-VI operates ?

Answer: 26

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The largest satellite system managed by 126 countries is international. Telecommunication Satellite Organization (INTELSAT).

The INELSAT-VI operates at microwaves frequencies of 4, 6, 11 and 14 Ghz.

Question: 27

What are geostationary orbit and geostationary satellites?

Answer: 27

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Geostationary Orbit: An orbit in which the time period of satellite is equal to the time period of spin motion of the earth is called geostationary orbit.

Geostationary Satellites: A satellite whose orbital motion is stationary along the earth is called geostationary satellite.

Question: 28

What are Artificial Satellites?

Answer: 28

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Artificial Satellites are the man-made objects that orbit around the Earth.

Question: 29

Why Einstein views of gravitation are preferred than Newton's views of gravitation? Explain briefly

Answer: 29

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Newton discovered the inverse square law of gravity. Einstein's theory also says that gravity follows an inverse square law (except in strong gravitational fields), but it gives us a physical picture of how gravity works. The bending of star light caused by the gravity of the Sun was measured during a solar eclipse in 1919, it was found to match Einstein's Prediction rather than Newton's.

Question: 30

How is artificial gravity created?

Answer: 30

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Artificial gravity is the gravity like effect produced in an orbiting spaceship to overcome weightlessness.To create artificial gravity the spaceship is set into rotation around its own axis. The astronaut then is presses towards the outer rim and exerts a force on the floor of the spaceship in much the same way as on the earth.

Question: 31

Explain how many minimum number of Geo-stationary satellites are required for global coverage of T.V transmission.

Answer: 31

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A geostationary satellite covers 120° of longitude. So the whole earth can be covered by three correctly positioned geostationary satellites.

Question: 32

Explain why earth's satellite despite of being freely falling object does not reach the earth.

Answer: 32

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To orbit the planet and not come crashing down, a spacecraft has to travel forward (tangential to Earth ) fast enough that it compensates for the fall downwards. The trajectory of its fall has the same curvature as earth's surface. So it will never reach the earth.

Question: 33

Write down application of communication satellites.

Answer: 33

33-35

A satellite communication system consist of three geo-stationary satellites.There are over 200 Earth stations which can transmit and receive signals.INTELSAT-VI operates at microwave frequencies 4, 4, 11 and 14 Ghz and has a capacity of 30,000 two way telephone circuits plus three TV channels.

Geo-stationary satellite are very useful for worldwide communication,weather observation, navigation, and other military uses.

Question: 34

What is Geo-stationay satellite? How many minimum number of geo-stationary satellites are required fro global coverage coverage of T.V transmission ?

Answer: 34

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S satellite whose orbital motion is stationary along the earth is called geostationary satellite. The time period of satellite is equal to the time period of spin motion of the earth.

A geostationary satellite covers 120° of longitude. So the whole earth can be covered by three correctly positioned geo-stationary satellites.

Question: 35

Define centripetal force; write its formula and unit.

Answer: 35

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11th Class Chapter five Physics Short Questions

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