Question

Two balls of different masses are thrown in the air with different velocities. While they are in the air then the acceleration of centre of mass of the system: (neglect air resistance)

• A. depends on the direction of the motion of two balls
• B. depends on the masses of the two balls
• C. depends of the magnitude of velocities of the two balls
• D. is equal to $g$

Answer 1

The correct option is D is equal to $g$

The motion of the center of mass of any system of particles is governed by Newton's second law, which is written as $\sum F_{ext}=M{a}_{cm}$
For both balls of masses $m_1,m_2$
One can write $m_{1}g+m_{2}g=(m_1+m_2)a_{cm}$
which gives, $a_{cm}=g$
Hence, option D is correct.