Name the force which is responsible for change in position or state of an object.

Mention the nature of motion of a body if its displacement$-$time graph is a straight line parallel to the time axis.

$A$ motorcyclist drives from $A$ to $B$ with a uniform speed of $30\, km\, h^{-1}$ and returns back with a speed of $20\, km\, h^{-1}$. Find its average speed (in $km\, h^{-1}$).

An electron moving with a velocity of $5 \times 10^{4} \, ms^{-1}$ enters into a uniform electric field and acquires a uniform acceleration of $10^{4} \, ms^{-2}$ in the direction of its initial motion.
$(i)$ Calculate the time in which the electron would acquire a velocity double of its initial velocity.
$(ii)$ How much distance the electron would cover in this time?

Derive the following equations for a uniformly accelerated motion:
$(i)$ $v = u + at$
$(ii)$ $S = ut + \frac{1}{2}at^2$
$(iii)$ $v^2 - u^2 = 2aS$, where the symbols have their usual meanings.

Draw the distance$-$time graph for the following situations:
$(a)$ When a body is stationary.
$(b)$ When a body is moving with a uniform speed.
$(c)$ When a body is moving with non$-$uniform speed.