9th Class Chapter 2 Physics Long Questions

Difference between scalars and vectors quantities.

Scalars Quantities: " A scalar quantity by its magnitude only." Explanation: A physical quantity which can be completely described by its magnitude is called a scalar. The magnitude of a quantity means its numerical value with an appropriate unit such as 2.5 kg, 40s , 1.8m, etc. Examples: Examples of scalars are mass, length, time speed, volume, work and energy. Vectors Quantity: " A vector quantity is described completely by magnitude and direction." Explanation: A vector can be described completely by magnitude along with its direction. It would be meaningless to describe vectors without direction Examples: Distance of a place from reference point is insufficient to locate that place. The direction of that place from reference point is also necessary to locate it. Examples of vectors are velocity, displacement, force, momentum, torque etc.

A cricket ball is hit vertically upwards and returns to ground 6s later. Calculate 1- maximum height reached by the ball. 2- Initial velocity of the ball. Given Data: t=6s =6/2 =3s h= ? Vi = ? Vf =0 g = -10ms-²

Solution: 2 Vf= Vi + gt Putting the values 0= Vi+(-10)(3) 0= Vi -30ms-¹ Vi=30ms-¹ 1 h= Vit + 1/2 gt² h=30(3) +1/2 (-10)(3)² = 90-90/4 = 90-45m h= 45m Ans'' ___

Differentiate between distance and displacement.

Distance: Length of a path between two points is called the distance between those points. Explanation: Let S be the Length of the curved path between two points A and B on it. Then S is the distance between points A and B. Displacement: "Displacement is the shortest distance between two points which has magnitude and direction." Explanation: Consider a body that moves from Point A to point B along the curved path. Joint points A and B by a straight line. The straight line AB gives the distance which is the shortest between A and B. This shortest distanced in a particular direction is called displacement. It is a vector quantity and is represented by d.

Given Data: Vi =0 g = 10ms-² t = 5s S=h=? Vf=?

Solution: h= Vit+ 1/2 gt² putting values h = 0x5+1/2(10)(5)² = 0+125 h=125m Vf²=2500m²s-² vVf² = v2500m²s-² eg.. ( root cut with power ²) Vf = 50ms-¹ Ans..

Define kinematics and explain rest and motion are relative

Kinematics: kinematics is the branch of mechanics which related to study of motion of objects without discussing the cause of its motion.

Explain the type of motion

There are three types of motion

What are scalars and vectors. How vectors are represented

Scalers: physical quantities that can be described completely by its magnitude only are called as scaler quantity

Define the terms related to motion, position, distance, displacement

Position: the term position describes the location of place or point with respect to some reference point called origin

Explain the term speed and velocity

Describe uniform speed and uniform velocity

Uniform speed: a body has uniform speed if it covers equal distance in equal interval of time however short the interval may be

Define and explain acceleration. also define uniform acceleration

Acceleration: acceleration is defined as the rate of change of velocity of a body. it is represent by a

what is graph. Explain the motion graphically

Graph: graph is a pictorial way or presenting information about the relation between various quantities. The quantities between which a graph is plotted are called variables

Explain the motion of freely falling bodies

Motion of freely falling bodies: Galileo was the first scientist to notice that all the freely falling objects have the same acceleration independent of their masses

Derive first equation of motion. or prove that vf = vi+at

consider a body moving with initial velocity vi in a straight line with uniform acceleration . Its velocity becomes vf after time t. The motion of body is described by speed time graph as shown in figure by line AB. The slope of line AB is acceleration a. speed time graph from the motion of a body is shown in figure

Derive second equation of motion

Consider a body moving with initial velocity vi in a straight line with uniform acceleration a . Its velocity becomes vf after time t. The motion of body is described by speed time graph by line AB. The slope of line Ab is acceleration a. The total distance covered by the body is shown by the shaded area under the line AB. Equations of motion can be obtained easily from this graph.

Derive third equation of motion

Consider a body moving with initial velocity vi in a straight line with uniform acceleration a . Its velocity becomes vf after time t. The motion of body described by speed time graph by line AB. The slope of line AB is acceleration a. The total distance covere by the body is shown by the shaded area under the line AB. Third equation of motion can be obtained easily from the graph.