Question

Martin (56 kg) and his sister (31kg) are rolling skating. when they are stationary, Martin pushes his sister causing her to move away from him at 1.96m/s. calculate martin's velocity.

Answer 1

Given

M = 56 kg

m = 31 kg

vm = 1.96m/s

Procedure

The law of momentum conservation can be stated as follows. For a collision occurring between object 1 and object 2 in an isolated system, the total momentum of the two objects before the collision is equal to the total momentum of the two objects after the collision.

`\begin{gathered} m*v_(om)+M*v_(oM)=m*v_(fm)+M*v_(fM) \\ 0=mv_(fm)+Mv_(fM) \\ 0=31*1.96m/s+56*v_(fM) \\ v_(fM)=(-31*1.96m/s)/(56) \\ v_(fM)=-1.085m/s \end{gathered}`

Martin's final velocity is -1.085 m/s