Question

Which of the following statement is correct ?

(a) The kinetic energy of a body during impact remains constant.

(b) The kinetic energy of a body before impact is equal to the kinetic energy of a body after impact.

(c) The kinetic energy of a body before impact is less than the kinetic energy of a body after impact.

(d) The kinetic energy of a body before impact is more than the kinetic energy of a body after impact.

This question was posed to me in an online interview.

I would like to ask this question from Kinetics of Motion in portion Kinematics & Kinetics of Motion of Machine Kinematics

Answer 1

Right choice is (d) The kinetic energy of a body before impact is more than the kinetic energy of a body after impact.

For explanation I would say: Total kinetic energy of the system before impact,

E1 = 1/2 m1 (u1)^2 + 1/2 m2 (u2)^2

When the two bodies move with the same velocity v after impact, then

Kinetic energy of the system after impact,

 E2= 1/2( m1 + m2) v^2

∴ Loss of kinetic energy during impact,

 EL = E1 – E2