How Does Twin Motion Affect Cart Direction?

[whoareyou]

Homework Statement

The Attempt at a Solution

My first attempt was that since one of the twins runs east at top speed (with both masses) then the cart moves west and then he jumps off. Then after the second twin runs with the same speed west, the cart (with only one mass this time and the same speed) would move east, and he'd jump off. So I decided that B should be the answer. Is that correct?

 

[Delphi51]

I know my intuition isn't good for this one! Definitely worth working out. Beware of the changing mass and the difficult choices for frame of reference.

 

[berkeman]

Homework Statement

The Attempt at a Solution

My first attempt was that since one of the twins runs east at top speed (with both masses) then the cart moves west and then he jumps off. Then after the second twin runs with the same speed west, the cart (with only one mass this time and the same speed) would move east, and he'd jump off. So I decided that B should be the answer. Is that correct?

I think that is the correct answer, but can you articulate why?