How Does Conservation of Momentum Apply in a Frictionless Sled Problem?

[PatsObi]

I'm stuck on this problem.

A sledge of mass 120 kg is at rest on a horizontal icy surface. A man of mass 70 kg stands at one end of the sledge so the initially the distance from the man to the shore is 20 m. The man now walks 3 m relative to the sledge, towards the shore. The he stops. Assuming the moves w/out friction, how far from the shore is the man when he stops.

THis is pretty much all i know:

70(Rm)+120(Rs)=0

where Rm and Rs are the distances from the man to the cm and the cm of the sledge to the cm respectfully.

 

[Shooting Star]

THis is pretty much all i know:

70(Rm)+120(Rs)=0

where Rm and Rs are the distances from the man to the cm and the cm of the sledge to the cm respectfully.

That is actually all you need, but with some understanding. Can you tell me what this eqn signifies? And how to find the CM of the system wrt the shore? After that, we can form the necessary eqns.

Also, the word you were looking for is "respectively", not respectfully.