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)?

$A$ ball is dropped from the roof of a tower of height $h$. The total distance covered by it in the last second of its motion is equal to the distance covered by it in the first three seconds. The value of $h$ in meters is $(g = 10\,m/s^2)$.

$A$ man throws balls with the same speed vertically upwards one after the other at an interval of $2\,s$. What should be the speed of the throw so that more than two balls are in the sky at any time? (Given $g = 9.8\,m/s^2$)

$A$ body falling from a high minaret travels $40 \ m$ in the last $2 \ s$ of its fall to the ground. The height of the minaret in meters is (take $g = 10 \ m/s^2$):

$A$ ball is thrown vertically upwards with a velocity of $19.6 \, m/s$ from the top of a tower. The ball strikes the ground after $6 \, s$. The height from the ground up to which the ball can rise is given by $\left(\frac{k}{5}\right) \, m$. The value of $k$ is ..... (use $g = 9.8 \, m/s^2$)

$A$ ball is dropped from a height of $90 \; m$ on a floor. At each collision with the floor,the ball loses one-tenth of its speed. Plot the speed-time graph of its motion between $t = 0$ to $12 \; s$.