A metal ball of mass 2 kg moving with speed of `36 km h^(-1)` has a head on collision with a stationary ball of mass 3 kg. If after collision, both the balls move together, then the loss in kinetic energy due to collision is 

Options

A. 40 J
B. 60J
C. 100 J
D. 140 J

Answer

B

Explanation

Applying principle of conservation of linear momentum , `m_1 u_1 + m_2u_2 = (m_1 + m_2) v`
`2 xx 10 + 3 xx 0 = (2 + 3) v :. v = 4 ms^(-1)`
Initial KE, `K_1 = 1/2 m_1u_1^2 = 1/2 xx 2 xx 10^2 = 100 J`
Final KE, `K_2 = 1/2 (m_1 + m_2) v^2 = 1/2 (2 + 3) xx 4^2 = 40 J`
`:. ` Loss in KE = `K_1 - K_2 = 100 - 40 = 60 J`.