A train is travelling at a speed of $90\, km h ^{-1}$. Breaks are applied so as to produce a uniform acceleration of $0.5\, m s ^{-2}$. Find how far the train will go before it is brought to rest.
Given $u=90 km h ^{-1}=5 \times \frac{90}{18}=25 m s ^{-1}, v=0$
$a=-0.5 m s ^{-1}, S =?$
Using
$v^{2}-u^{2}=2 a S$
$0-(25)^{2}=2 \times-0.5 \times 5$
or $S =625 m$
An object is dropped from rest at a height of $150\, m$ and simultaneously another object is dropped from rest at a height $100 \,m$. What is the difference in their heights after $2\,\sec $ if both the objects drop with same accelerations ? How does the difference in heights vary with time ?
A girl walks along a straight path to drop a letter in the letterbox and comes back to her initial position. Her displacement-time graph is shown in Fig. Plot a velocity - time graph for the same.
$(a)$ Define uniform circular motion.
$(b)$ Is the uniform circular motion an accelerated motion? Give reasons for your answer.
A racing car has an acceleration of $4\, m s ^{-2} .$ What distance will it cover in $20$ seconds after start ?
Distinguish between terms distance and displacement.