Question

Two identical bodies moving in opposite direction with same speed, collided with each other. If the collision is perfectly elastic then

• A. after the collision both comes to rest
• B. after the collision first comes to rest and second moves in the same direction with a speed 2v
• C. after collision they recoil with same speed
• D. all the above are possible

Answer 1

Answer: (C)

after collision they recoil with same speed

$mv+m(-v)=m{v}_1+m{v}_2=0\Rightarrow v_1+v_2=0$
$\frac{v_1-v_2}{v-(-v)}=1\Rightarrow v_1-v_2=2v$

$thus,v_1=v{v}_2=-v$