The speed-time graph for a car is shown is Fig.

$(a)$ Find how far does the car travel in the first $4,sec$. Shade the area on the graph that represents the distance travelled by the car during the period.

$(b)$ Which part of the graph represents uniform motion of the car ?

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

A motorboat starting from rest on a lake accelerates in a straight line at a constant rate of $3.0\, m s^{-2}$ for $8.0 \,s$. How far does the boat travel (in $m$) during this time ?

A train is travelling at a speed of $90\, km \,h^{-1}$. Brakes are applied so as to produce a uniform acceleration of $- 0.5\, m s^{-2}$. Find how far(in $m$) the train will go before it is brought to rest.

A ball is gently dropped from a height of $20\, m$. If its velocity increases uniformly at the rate of $10\, m s^{-2}$, with what velocity will it strike the ground? After what time will it strike the ground ?