Question

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

Options

• depends on the direction of the motion of the balls 

• depends on the masses of the two balls

• depends on the speeds of the two balls

• is equal to g. 

Answer 1

 is equal to g 
The acceleration of the centre of mass of two balls having masses m₁ and m₂ is given by 
\[a_{cm} = \frac{m_1 \vec{a}_1 + m_2 \vec{a}_2}{m_1 + m_2}\]
\[ = \frac{m_1 g + m_2 g}{m_1 + m_2}\]
\[ = g\]