A point mass of 1kg collides elastically with a stationary point mass of 5kg. After their collision, the 1kg mass reverses its direction and moves with a speed of 2m/s. Which of the following statement(s) is (are) correct for the system of these two masses?
a) Total momentum of the system is 3kg m/s
b) Momentum of 5kg mass after collision is 4kg m/s
c) Kinetic energy of the centre of mass is 0.75 J
d) Total kinetic energy of the system is 4J
Given point
Mass of m=1kg
Mass of stationary point m=5kg
Speed v=2m/s
By conservation of linear momentum
2. As we know, the coefficient of restitution is given by for elastic collision. Using this we get,
Using Equation (i) and (ii), we have and
Initial momentum of the system,
Kinetic energy of the centre of mass
KE of system=
Therefore, the correct answer is (B).