Why did both objects fall at the same speed during the second trial?

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.

1.what is where an object is located 2. what is how fast an objects speed is changing 3. what is how fast an object is moving

Acar is traveling 35 mph on a smooth surface . if a balanced force is applied to the car what happens?