NCERT Class-9 Science Solutions: Chapter 8-Motion Part 3

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Short Answer Questions

Question 12:

The displacement of a moving object in a given interval of time is zero. Would the distance travelled by the object also be zero? Justify you answer.

Answer:

No It is not true that if displacement is zero. Therefore, distance would be zero. displacement is the Shortest Distance traveled by the object and distance is the Total Distance traveled by the object.

Question 13:

How will the equations of motion for an object moving with a uniform velocity change?

Answer:

Acceleration

Question 14:

A girl walks along a straight path to drop a letter in the letterbox and comes back to her initial position. Her displacement–time graph is shown in Fig. Plot a velocity–time graph for the same.

Image displacement–time graph (Q)

Image Displacement–Time Graph (Q)

Image displacement–time graph (Q)

Answer:

Image displacement–time graph (A)

Image Displacement–Time Graph (A)

Image displacement–time graph (A)

Question 15:

A car starts from rest and moves along the with constant acceleration for . If it then continues with constant velocity, what distance will the car cover in since it started from the rest?

Answer:

The distance travelled in first

At this point the velocity

Therefore, the distance covered in last four seconds,

Thus, the total distance

Question 16:

A motorcyclist drives from A to B with a uniform speed of and returns back with a speed of . Find its average speed.

Answer:

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