Question

A ball is thrown upward from the ground with an initial speed of 25 m/s; at the same instant, another ball is dropped from a building 15 m high. After how long will the balls be at the same height above the ground?

Answer 1

$Y_1=(1/2)gt^2$

$Y_2=25t-(1/2)gt^2$

$Y_1+Y_2=15$

Solving the above three equations we get t= 0.6 second