A motor bike running at $90\, km h ^{-1}$ is slowed down to $18 \,km h^{-1}$ in $2.5\, s$. Calculate
$(i)$ acceleration
$(ii)$ distance covered in the time it slows down
$u=90 km h ^{-1}=25 m s ^{-1} ; v=18 km h ^{-1}=5 m s ^{-1}$
$t=2.5 s ; a=? ; S =?$
$(i)$ Applying $v=u+a t$
$5=25+a \times 2.5$
$-20=2.5 \times a$
Or $a=\frac{-20}{2.5}=-8 m s ^{-2}$
$(ii)$ Applying $v^{2}-u^{2}=2 a S$
$(5)^{2}-(25)^{2}=2 \times(-8) \times S -600=-16 S$
or $S=\frac{600}{16}=37.5 m$
State the type of motion represented by the given graph.
What can you say about the motion of an object whose distance time graph is
$(i)$ a straight line, parallel to the time axis ?
$(ii)$ a straight line passing through the origin making an angle with the time axis ?
A piece of stone is thrown vertically upwards. It reaches its maximum height in $3$ second. If the acceleration of the stone be $9.8\, m s ^{-2}$ directed towards the ground, calculate the initial velocity of the stone with which it is thrown upwards. Find the maximum height attained by it.
The direction of acceleration of an object moving in a circular path is
An electric train is moving with a velocity of $120\, km h^{-1} .$ How much distance will it corer in $30 \,s$ ?