Question

Two small balls having the same mass & charge & located on the same vertical at heights  h₁ &h₂ are thrown in the same direction along the horizontal at the same velocity v. The 1^st ball touches the ground at a distance l from the initial vertical. At what height will the 2^nd ball be at this instant? The air drag & the charges induced should be neglected

Answer 1

Consider the two balls of system, the only external force is gravitational force. Initial position of COM is at h₁ +h₂/2. The vertical distance moved by

If the COM is at H, and one particle is on ground then the height of the other will be at height