Question

Two balls are thrown simultaneously in air. The acceleration of the centre of mass of the two balls while in air 

(a) depends on the direction of the motion of the balls 

(b) depends on the masses of the two balls 

(c) depends on the speeds of the two balls 

(d) is equal to g.

Answer 1

(d) is equal to g.

Explanation: 

Since there is no force in the horizontal direction there will be no acceleration of CoM in the horizontal direction whatever be the direction, mass or speed of the two balls. Only force is the gravitational force hence acceleration of CoM will be acceleration due to gravity g.