$A$ stone is dropped from the top of a building. When it crosses a point $5 \, m$ below the top,another stone starts to fall from a point $25 \, m$ below the top. Both stones reach the bottom of the building simultaneously. The height of the building is ..... $m$.

$A$ body is thrown vertically upwards with a velocity of $35 \ m/s$ from the ground. The ratio of the speeds of the body at times $3 \ s$ and $4 \ s$ of its motion is (Acceleration due to gravity $= 10 \ m/s^2$)

$A$ stone is thrown with an initial speed of $4.9 \, m/s$ from a bridge in a vertically upward direction. It falls down into the water after $2 \, s$. The height of the bridge is .......... $m$.

Can a particle moving in a straight line have zero velocity and non-zero acceleration at any instant? Give an example.

$A$ paratrooper jumps from an aeroplane and opens a parachute after $2 \ s$ of free fall and starts decelerating with $3 \ m/s^2$. At $10 \ m$ height from the ground,while descending with the help of the parachute,the speed of the paratrooper is $5 \ m/s$. The initial height of the aeroplane is . . . . . . $m$. $(g = 10 \ m/s^2)$

When a particle is thrown vertically upwards,its velocity at one third of its maximum height is $10 \sqrt{2} \, m/s$. The maximum height attained by it is .......... $m$.