$A$ stone thrown upward with a speed $u$ from the top of a tower reaches the ground with a velocity $3u$. The height of the tower is (in $u^2/g$)

$A$ ball is thrown vertically upward with an initial velocity of $150\,m/s$. The ratio of velocity after $3\,s$ and $5\,s$ is $\frac{x+1}{x}$. The value of $x$ is $...........$ Take $g=10\,m/s^2$.

$A$ stone is dropped from a height $h$. It hits the ground with a certain momentum $P$. If the same stone is dropped from a height $100\%$ more than the previous height,the momentum when it hits the ground will change by ........... $\%$.

$A$ tennis ball is released from a height $h$ and after freely falling on a wooden floor,it rebounds and reaches a height $\frac{h}{2}$. The velocity versus height of the ball during its motion may be represented graphically by (graphs are drawn schematically and not to scale):

Two balls of the same size,but where the density of one is greater than that of the other,are dropped from the same height. Which ball will reach the Earth first (air resistance is negligible)?

Due to the presence of air resistance, if a body dropped from a height of $20 \ m$ reaches the ground with a speed of $18 \ m/s$, then the time taken by the body to reach the ground is nearly (in $s$)