How fast must a 100 kg object be going in order for it to stop a 200 kg object traveling at 10 km/hr when the two objects collide head on?

P1i+p2i =p1f +p2f where p is momentum and i denotes initial, f denotes final, and 1 and 2 refers to the object number. If the object stops, their velocity is 0 and p1f and p2f also equal 0.

p=mass x velocity

We have p1i=-p2i

100v1i=-(200) (-10÷3.6)

Note: 10÷3.6 is 10km/hr in m/s
Note: The velocity of the second object ifs negative because I said the velocity of the first object was positive and the second object is travelling in the opposite direction

So v1i=20/3.6=5.56m/s