Question

two similar spheres each of mass m and travelling with speed v, are moving towards each other. The spheres have a head on elastic collision. Which statement is correct? And reason?

A. The spheres stick together on impact
B. The total K.E before impact is zero
C. The total K.E after impact is mv²
D. The total momentum before impact is 2mv​

Answer 1

The total K.E after impact is mv².(option c)

Explanation,

• It is an elastic collision, therefore spheres will not stick to each other.

• Before the collision, kinetic energy of the system is $2* [\frac{1}{2}mv^{2} ]$ = $mv^{2}$

• Being elastic collision, there is no loss of energy. Total energy before and after collision will remain the same, that is  $mv^{2}$. ( Energy here is only in the form of kinetic energy)

• Bodies with equal mass and equal velocity are travelling in opposite direction, total momentum of the system will be zero.