10 kg ball is dropped from a height of 10 m. What is the speed of the ball just before it reaches the ground?

Q. An object is dropped from a height of $20\text{m}$. If a plane mirror is lying on the floor with the reflecting surface facing the object. The speed of image of the ball with respect to the ball just before striking the mirror will be
$($Take $g=10{\text{m/s}}^2)$

Q. A $10kg$ ball is dropped from a height of $10m$. Find (a) the initial potential energy of the ball, (b) the kinetic energy just before it reaches the ground, and (c) the speed just before it reaches the ground.

Q. A ball of mass $10\text{kg}$ initially at rest starts moving under the influence of a constant force $50\text{N}$. Ball covers $10\text{m}$ before colliding a heavy wall which is moving towards the ball with speed $10\text{m/s}$ as shown in figure. If force stops acting on ball just before collision and collision is perfectly elastic, find the velocity of ball after collision.