Help me pls Explain what happens when two light waves travelling from the same direction of displacement meet.

Mutt and jeff are running along a path each pushing a cart loaded with rocks. if mutt's wagon has a mass two times greater than jeff's and they want to stay together, arriving at their destination at the same time, what must happen? a) jeff should slow down so mutt can catch up. b) mutt must use half as much force to push his cart. c) mutt must use twice as much force to push his cart. d) mutt and jeff will use the same force, but mutt will take bigger steps.

What are two different ways you could find the value of a? explain these methods.

Aball is thrown horizontally from a cliff at 8m/s .in what direction is the ball moving 2s later?