Question

A ball A is thrown vertically upwards with an inital speed v. A second ball B is thrown vertically upwards from same point at same speed n second later. The two meet one another before returning back to the point of projection. The maximum value of n is

(1) v/g

(2) 2v/g

(3) v/2g

(4) 3v/2g

Answer 1

 (2) 2v/g

Choosing the point of projection of balls as origin of co-ordinates and vertically upward direction as direction of +z – axis the instantaneous position co-ordinates z₁ and z₂ of th two balls is

When the two balls meet one another z₁ = z₂

The first ball will hit ground at t = 2v/g. The maximum value of t is 2v/g. 

Hence,