Page No 107: - Chapter 8 - Motion - Ncert Solutions class 9 - Science

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Question 1:

What is the nature of the distance−time graphs for uniform and non-uniform motion of an object?

Answer:

The distance−time graph for uniform motion of an object is a straight line (as shown in the following figure).

The distance−time graph for non-uniform motion of an object is a curved line (as shown in the given figure).

Question 2:

What can you say about the motion of an object whose distance−time graph is a straight line parallel to the time axis?

Answer:

When an object is at rest, its distance−time graph is a straight line parallel to the time axis.

A straight line parallel to the x-axis in a distance−-time graph indicates that with a change in time, there is no change in the position of the object. Thus, the object is at rest.

Question 3:

What can you say about the motion of an object if its speed−time graph is a straight line parallel to the time axis?

Answer:

Object is moving uniformly.

A straight line parallel to the time axis in a speed−time graph indicates that with a change in time, there is no change in the speed of the object. This indicates the uniform motion of the object.

Question 4:

What is the quantity which is measured by the area occupied below the velocity−time graph?

Answer:

Distance

The graph shows the velocity−time graph of a uniformly moving body.

Let the velocity of the body at time (t) be v.

Area of the shaded region = length × breath

Where,

Length = t

Breath = v

Area = vt = velocity × time …(i)

We know,

Velocity = DisplacementTIme

∴ Displacement = Velocity × Time…(ii)

From equations (i) and (ii),

Area = Displacement

Hence, the area occupied below the velocity−time graph measures the displacement covered by the body.