Question

A $3.0kg$ lump of clay is moving to the left at $4.0m/s$. It collides in a perfectly inelastic collision with a $6.0kg$ lump of clay moving to the right at $2.0m/s$.
What is the total kinetic energy after the collision?

• A. $62J$
• B. $36J$
• C. $25J$
• D. $12J$
• E. $0J$

Answer 1

Answer: (E)

$0J$

Given - $m_1=3.0kg,m_2=6.0kg,v_1=-4.0m/s,v_2=2.0m/s$ ,

let the combined velocity after collision is $v$

by the law of conservation of linear momentum ,

net momentum before collision = net momentum after collision ,

$p_1+p_2=p$

$m_1{v}_1+m_2{v}_2=(m_1+m_2)v$

or $3.0\times -4.0+6.0\times 2.0=(3.0+6.0)v$

or $-12+12=9v$

or $v=0m/s$

therefore kinetic energy after collision , $K=1/2m{v}^2=0J$