A point mass of `1 kg` collides elastically with a stationary point mass of `5 kg`. After their collision, the `1kg`, mass reverses its direction and moves with a speed of `2ms^(-1)` . Which of the following statement(s) is (are) correct for the system of these two masses?
A. total momentum of the sytem is 3 kg `ms^(-1)`
B. momentum of 5 kg mass after collision is 4 kg `ms^(-1)`
C. KE of the centre of mass is 0.75 J
D. totak KE of the system is 4J
