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.
Here, $t=3 s , u=?, v=0, h=?, a=g=-9.8 m s ^{-2}$
$u=v-a t$.
$=0-(-9.8) \times 3$
$=29.4 m s ^{-1}$
$h=u t+\frac{1}{2} g t^{2}$
$=29.4 \times 3+\frac{1}{2} \times(-9.8) \times 3^{2}$.
$=88.2+(-44.1)$
$=44.1 m$
Why does (second)$^{2}$ occur in the unit of acceleration ?
There are 5 houses on a street, $A, B, C, D$ and $E$. For all cases, assume that positions to the right are positive.
$(i)$ Draw a frame of reference with house $A$ as the origin and the positions of houses $B, C, D$ and $E$.
$(ii)$ You live in house $C.$ What is your position relative to house $E$ ?
$(iii)$ What are the positions of houses $A$ and $D$, if house $B$ is taken as the reference point ?
Identify what do the graphs shown below indicate ?
What is the slope of the displacement $-$ time graph when the body has uniform motion ?
Ali while driving to school computes the average speed for his trip to be $20\, km h^{-1}$. On his return trip along the same route there is less traffic and the average speed is $30\, km h^{-1} .$ What is the average speed for Ali's trip ?