A point mass of 1 kg collides elastically with a stationary point mass of 5 kg. After their collision, the 1 kg mass reverses its direction and moves with a speed of 2 ms−1 . Which of the following statement(s) is (are) correct for the system of these two masses? [2010]
a. Total momentum of the system is 3 kg ms−1
b. Momentum of 5 kg mass after collision is 4 kg ms−1
c. Kinetic energy of the centre of mass is 0.75 J
d. Total kinetic energy of the system is 4 J