Kinematics I , FBISE 9th Class Physics Chapter 2

New book Complete Solution of 9th Class Physics Short question of 9th class physics for federal board , 9th class physics numerical notes

SHORT RESPONSE QUESTIONS

Q1. In a park, children are enjoying a-ride on Ferris wheel as shown
What kind of motion the big wheel has and what kind of motion the
riders have?

Ans : Riders are enjoying a ride on a big wheel. The motion of the riders is in circle so the motion of the riders is called circular motion. Big wheel is rotating about its axis so the motion of the wheel is called rotatory motion.

Q2. A boy moves for some time, give two situations in which his displacement is zero but covered distance is not zero?

Ans : Yes, the displacement can be zero even if the distance is not zero.

Example: Circular motion of a body results in zero displacements but the distance cannot be zero.

Situation1 : When boy completes his journey along circular path then his displacement is zero because the starting and ending point is same but distance is not zero.

Situation 2 : If a boy starts its journey on a straight line from point A to B is 5m.  such then  and comes back from point B to A is 5m. then its displacement is zero because starting and ending point is same but distance is 5+5 = 10m

Q3. A stone tied to string whirling in circle , what is the direction of its  velocity at any instant ?

1 Side riew 2 Top view

Ans : The direction of velocity at any instant of a stone tied to string whirling in a circle is always tangent to the circle. Whenever the string is cut, the stone never flies away directly away from the whirled as centrifugal force would imply. the circle. Instantaneous velocity of stone is acting as tangent to the circle.

Q4. Is it possible to accelerate an object without speeding it up or slowing it down?

Ans: Acceleration is defined as the rate of change in velocity. It implies that, if the velocity is constant then there is no acceleration. knowing whether an object is accelerated without speeding up or slowing down:

l. Yes, an object can be accelerated without speeding up or slowing down.

ii. We know that acceleration is referred as the rate of change of velocity and the velocity is the speed in a particular direction and is a vector quantity.

ii. So, if the velocity can either changes its speed or direction, there is some acceleration.

Iv. Thus, if we change the direction, and not the speed, we are still accelerating. Hence, an object can be accelerated without speeding up or slowing down.

Q5. Can a car moving towards right have direction of acceleration towards left?

Ans: Yes, it is possible to have acceleration opposing direction of velocity.

Explanation:

If a car is moving towards right then direction of velocity and acceleration is same ie toward the right. We apply brakes on the car then its speed decreases and declaration is produced in it. In this case the direction of velocity is towards the right but the direction of acceleration is towards the left.

Q6. With the help of daily life examples, describe the situations in which:

a. acceleration is in the direction of motion.

b. acceleration is against the direction of motion.

c. acceleration is zero and body is in motion.

Ans :

a. Acceleration in the direction of motion

Car Accelerating on a Highway: When you press the accelerator pedal of a car while driving on a highway, the car accelerates in the same direction as its motion.

b. Car Braking to Stop:

When a car applies the brakes to come to a stop, the acceleration is against the direction of motion. As the car slows down, its velocity vector points in the direction of its motion, but the acceleration vector points in the opposite direction, towards the direction it’s trying to stop.

c. Acceleration is zere and body is in motion:

Car moving at Constant Speed on a Straight Track: When a train is moving al a constant speed along a straight track with its change in its velocity, its acceleration is zero.

Q7. Examine distance-time graph of a motorcycirst (as shown) what dose this graph tell us about the speed of motorcyclist? Also plot its velocity-time graph?

Ans:

Ans: The given distance-time graph shows that the motorcyclist is moving with uniform speed.The given graph shows that the motorcyclist is travelling equal distances in equal intervals of time, which gives uniform speed.

velocity-time graph

Q8. Which controls In the car can produce acceleration or deceleration in It?

Ans: If the speed of a car is increasing then it is called acceleration. We use accelerator to increase the speed of the car which produces acceleration.

If the speed of the car is decreasing then it is called deceleration. We use brakes to decrease the speed of the car which produces deceleration in the car.

Q9. If two stones of 10 kg and 1kg are dropped from a 1km high tower. Which will hit the ground with greater velocity? Which will hit the ground first? (Neglect the air resistance)

Ans. If two stones of 10kg and 1kg dropped from a 1km high tower then the stones of 10kg hit the ground the with greater velocity. Because the force with which Earth attract the body towards its centre is equal to the weight of the object.

So the stone having mass 10kg will hit the ground with greater velocity. If we neglect air resistance then both the stones will reach on the ground at’same time.

Q10. A 100g ball is just released (from rest) and another is thrown downward with velocity of 10 m/s, which will have greater acceleration? (Neglect the air resistance)

Download FBISE 9th Class Physics Numerical Chapter 2