Question

From a building two balls A and B are thrown such that A is thrown upwards and B downwards (both vertically). If $v_A$ and $v_B$ are their respective velocities on reaching the ground, then

• A. $v_A>v_B$
• B. $v_A=v_B$
• C. $v_A<v_B$
• D. Their velocities depend on their masses.

Answer 1

The correct option is B $v_A=v_B$

As the ball moves down from height 'h' to ground the P.E. at height 'h' is converted to K.E. at the ground (Applying Law of conservation of Energy).
Hence, $\frac{1}{2}{m}_A{v}_A^2=m_A{gh}_{A}or{v}_A=\sqrt{2gh}$
Similarly, $v_B=\sqrt{2gh}or{v}_A=v_B$