Question

A wagon containing two boxes of gold and having a mass of 400 Kg altogether has been cut loose from the horses by an outlaw when the wagon is up on slope as in the sketch. Assume that the wagon rolls down the road with negligible friction. The outlaw plans to have the wagon rolls back down the slope and across the level ground and then crash into a canyon where his confederates wait. But in a tree L = 30 m from the cliff wait Batman of mass 80 Kg and Robin of mass 70 Kg (they both made A in Phys 1401). They drop together vertically into the wagon as it passes beneath them.

1. Let us now assume that Batman and Robin have no cliff to worry about. They decided to throw out a big chunk of gold so that the wagon will reverse its direction.

To which direction they should throw the gold?

Answer 1

They should throw the gold in the direction in which the wagon is moving. To take advatage of the principle of conservation of momentum, they need to create momentum by throwing the gold in a direction that is opposite to the direction in which they want their wagon to move. They want the wagon to move away from the canyon tree, by throwing the gold in the direction of the canyon tree, they create some momentum in that direction, to counter that a momentum(of wagon) will be created in the opposite direction, which will help the wagon to reverse it's direction.