The total mass of the wagon, rider, and rock is 80.0 kg. The mass of the rock is 0.400 kg. Initially the wagon is rolling forward at a speed of 0.600 m/s. Then the rock is thrown with a speed of 12.0 m/s. Both speeds are relative to the ground.
What is the final speed vf of the wagon after the rock is thrown forward?
What is the final speed vf of the wagon after the rock is thrown backward?