Question

A heavy steel ball of mass greater than 1 kg moving with a speed of 2$m\sec^{- 1}{}$collides head on with a stationary ping-pong ball of mass less than 0.1 gm. The collision is elastic. After the collision the ping-pong ball moves approximately with speed

• A. $2m\sec^{- 1}{}$
• B. $4m\sec^{- 1}{}$
• C. $2 \times 10^{4}m\sec^{- 1}{}$
• D. $2 \times 10^{3}m\sec^{- 1}{}$

Answer 1

Answer: (B)

$4m\sec^{- 1}{}$

Answer 2

We know that when heavier body strikes elastically with a lighter body then after collision lighter body will move with double velocity that of heavier body. i.e. the ping pong ball move with speed of $2 \times 2 = 4 \mathrm {~m} / \mathrm { s }$