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Study the speed-time graph of a car given below and answer the questions that follow
$(i)$ What type of motion is represented by $OA$ ?
$(ii)$ What type of motion is represented by $A B$ ?
$(iii)$ What type of motion is represented by $BC$ ?
$(iv)$ What is the acceleration of the car from $O$ to $A$ ?
$(v)$ What is the acceleration of the car from $A$ to $B$ ?
$(vi)$ What is the retardation of car from $B$ to $C$ ?
Solution
$(i)$ Velocity$-$time graph is a straight line inclined to the time axis from $0$ to $A$. This represents a uniformly accelerated motion.
$(ii)$ Velocity$-$time graph is a straight line parallel to time axis from $A$ to $B$. This represents uniform motion.
$(iii)$ The velocity$-$time graph is a straight line from $B$ to $C$ having a negative slope. This represents a uniformly retarded motion.
$(iv)$ Change in velocity $=40-0=40 m s ^{-1}$
Change in time $=10-0=10 s$
$a=\frac{\text { Change in velocity }}{\text { Change in time }}$
$=\frac{40}{10}=4 m s ^{-2}$
$(v)$ Since motion is uniform $a=0$
$(vi)$ Change in velocity $=0-40$
$=-40 m s ^{-1}$
Change in time $=50-30=20 s$
