A body of mass 2 kg moving with a velocity of 6 m/s strikes in elastically another body of same mass at rest. The amount of heat evolved during collision is:

Options

A. 36 J
B. 18 J
C. 9 J
D. 3 J

Answer

B

Explanation

`m_1u_1 + m_2u_2 = (m_1 + m_2) V , 2 xx 6 + 2 xx 0 = (2 + 2) V`
`V = 3 ms^(-1) , E = 1/2 (m_1 + m_2) V^2 = 1/2 xx 4 xx 9 = 18 J`
Initial KE =`1/2 mv^2 = 1/2 xx 2 xx 6^2 = 36 J`
`therefore ` heat evolved = `36 - 18 =18 J`