The distance$-$time graph of a body is parallel to the time axis. The body is

Give an expression for the speed of an athlete if he takes time $t$ to complete one round of a circular track of radius $r$.

By giving an example,prove that rest and motion are relative terms.

The graph given below is the distance-time graph of an object.
$(i)$ Find the speed of the object during the first four seconds of its journey.
(ii) How long was it stationary?
(iii) Does it represent a real-life situation? Justify your answer.

The distance-time graph of a body is a straight line inclined to the time axis. The body is in:

Ravi told his friend that his house is $1 \,km$ toward south from the main Post Office. Express the displacement and the distance moved by the friend from the Post Office when he arrives at Ravi's house. Mention the reference point chosen by you.