Four speed$-$time graphs are shown below

Which graph represents the following case ?

$(i)$ A ball thrown vertically upwards and returning to the hand of the thrower ?

$(ii)$ A body decelerating to a constant speed and then accelerating.

What is the nature of motion of a particle depicted by following displacement$-$time graphs ?

A person is running along a circular path in a park.

$(a)$ At what point he changes his direction while running ?

$(b)$ If he covered half of the circular path, what will be his displacement ? Draw a diagram showing it.

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 $km\, h^{-1}$).

$(a)$ Differentiate acceleration from velocity.

$(b)$ Can a body have acceleration without change in magnitude of velocity ? Explain with an example.

$(c)$ A motor boat starting from rest on a lake accelerates in a straight line at a constant rate of $3\, m s ^{-2}$ for $8 \,s$. How far does the boat travel during this time ?