CBSE 9th Physics Tutorials | Motion-Long Answer Type Question

September 21st, 2015 by Amit Thakur No comments »

Motion-Long Answer Type Question

Question 1. The following is the distance-time table of a moving car.

Time Distance Time Distance
10.05 am 0km 11.00 am 26 km
10.25 am 5 km 11.10am 28 km
10.40 am 12km 11.25 am 38 km
10.50 am 22 km 11.40 am 42 km

(i) Use a graph-paper and plot the distance traveled by the car versus time,

(ii) When was the car traveling with the greatest speed.:

(iii) What is the average speed of the car?

(iv) What is the speed between 11.25 am and 11.40am.

(v) During a part of the journey, the car was forced to slow down to 12 km/h, At what distance did this happen?

Answer (i)

The distance-time graph for the motion of the car is as shown in the figure given below

clip_image002

Answer (ii)

The car is traveling with maximum speed between 10.40 am and 10.50 am as during this time the distance-time graph has maximum slope. Here

image

Question 2. What types of motion are represented by the following velocity-time graphs?

clip_image014

clip_image016

Answer.

(a) The body has uniform velocity.

(b) The body has uniform acceleration and its initial velocity is zero.

(c) The body has some initial velocity and is under uniform retardation.

(d) The body has some initial velocity and uniform acceleration.

(e) The body has zero initial velocity and it has variable acceleration.

(f) The body is at rest from O to A, it has uniform acceleration from A to B, it has uniform velocity from B to C and from C to D, the body is under uniform retardation.

Question 3. A circular track has a circumference of 3140 m with AB as one of its diameter. A scooter moves from A to B along the circular path with a uniform speed of 10 m/s. Find distance covered by the scooter,displacement of the scooter, and time taken by the scooter in reaching from A to B.

Answer.

image

CBSE 9th Physics Tutorials | Motion-Very Short Answer Type Questions

September 21st, 2015 by Amit Thakur No comments »

Motion-Very Short Answer Type Questions

Question 1. when graph is parallel to time axis, what can you say about the motion?

Answer.

The body remains at rest.

Question 2. What is the value of acceleration, if v-t graph is a straight line parallel to the time axis?

Answer.

Zero, since slope is zero.

Question 3. Under what condition, the distance covered by a particle is equal to the magnitude of
displacement of particle?

Answer.

This happens when the body moves with a constant velocity.

Question 4. Is it possible that the average velocity of a particle is zero when its average speed is not
zero?

Answer.

This occurs when the particle returns to the starting point.

Question 5. What is meant by a point object? Give some examples.

Answer.

Whenever the size of the object is much smaller than the distance it moves in a given time interval, the size of the object can be neglected. Then the object may be regarded as the point object. Examples: (i) A car covering a distance of 10 km can be treated as a point object, (ii) Earth can be regarded as a point object for studying its motion around the sun.

Question 6. Can an object be at rest as well as in motion at the same time?

Answer.

Yes. An object may be at rest relative to one object and at the same time it may be in motion relative to another object.

Question 7. Can the average speed of a moving body ever be zero?

Answer.

No, speed, being a scalar quantity, is always positive. So its average speed can never be zero.

Question 8. A body is moving with a velocity of 10 m/s. If the motion is uniform, what will be the velocity after10 s?

Answer.

As the motion is uniform, the velocity remains equal to 10 m/s even after 10 s.

Question 9. Define velocity. What is its SI unit?

Answer.

The distance traveled by a body per unit time in given direction is called its velocity. The SI unit of velocity is m/s.

Question 10. Can the speed of a body vary if its velocity is constant?

Answer.

No. When the velocity of a body is constant, its speed is also constant.

Question 11. Can a body have constant speed but variable velocity?

Answer.

Yes. For example, a body in uniform circular motion has constant speed but its velocity changes at every point due to the change in the. direction of motion.

Question 12. What is the SI unit of retardation?

Answer.

m/s2.

Question 13. What is acceleration of a body moving with uniform velocity?

Answer.

Zero.

Question 14. If the acceleration of the particle is constant in magnitude but not in direction, what type of path does the body follow?

Answer.

Circular path.

Question 15. A ball is thrown up in air. What is the acceleration and velocity at the instant it reaches its highest point?

Answer.

Acceleration is 9.8 m/s2 acting downwards and velocity is zero.

Question 16. A car travels 1 km and returns back to the same point in a different path. What is the average velocity.

Answer.

Zero. Since total displacement is zero.

Question 17. Give an example of a motion in which the acceleration is in the direction of motion.

Answer.

When a body falls from the roof of a house, then the acceleration of the body is in the direction of motion.

Question 18. Give an example of a motion in which the acceleration is against the direction of motion.

Answer.

When a body is thrown upward, then the acceleration is against the direction of motion.

Question 19. What does the slope of a speed-time graph indicate?

Answer.

Acceleration

Question 20. What do we get from the area between the speed- time graph of a body and the time-axis?

Answer.

Distance traveled by the body.

Question 21. If the velocity-time graph of a body is a line parallel to the time-axis, what would be the acceleration of the body?

Answer.

Zero, because the body possesses uniform velocity.

Question 22. A satellite goes round the earth in a circular orbit with constant speed. Is the motion accelerated?

Answer.

Yes.

Question 23. If the displacement of a body is zero, is the distance covered by it necessarily zero?

Answer.

No, it is not necessary that the distance covered by a body is zero when its displacement is zero.

Question 24. Can the displacement be greater than the distance traveled by an object?

Answer.

No, the displacement of an object can be either equal to or less than the distance traveled by the objects.

Question 25. Under what condition will the distance and displacement of a moving object have the same
magnitude?

Answer.

When the object moves along the same straight line in the same fixed direction.