State whether the following statement is true or false:
Velocity and speed are measured in different units.

Study the given velocity-time graph and answer the following questions:
$(i)$ Which part of the graph shows accelerated motion?
$(ii)$ Which part of the graph shows retarded motion?
$(iii)$ Calculate the distance travelled by the body in the first $4 \ s$ of the journey graphically.

What is meant by free fall? Two bodies,one of mass $1\,g$ and other of mass $1\,kg$,are dropped from the same height in a vacuum. Compare the two time intervals in which the two bodies will hit the ground.

$A$ truck running at $90 \text{ km h}^{-1}$ is brought to rest over a distance of $25 \text{ m}$. Calculate the retardation and time for which brakes are applied.

Give examples to distinguish:
$(i)$ Distance and displacement.
$(ii)$ Speed and velocity.
$(iii)$ Acceleration and retardation.

The following figure is the speed-time graph for a rocket from the moment when the fuel starts to burn,i.e.,at time $t=0$.
$(a)$ State the acceleration of the rocket at $t=0$.
$(b)$ State what happens to the acceleration of the rocket between $t=5 \, s$ and $t=60 \, s$.
$(c)$ Calculate the acceleration of the rocket at $t=80 \, s$. Give a reason for your answer.
$(d)$ The total mass of the rocket at $t=80 \, s$ is $1.6 \times 10^{6} \, kg$. Calculate the resultant force on the rocket at this time. Give a reason for your answer.