100 m Rail car A 5000 kg Rail car B 2000 kg Rail car A (5000 kg) collides with stationary rail car B (2000 kg). After the collision the two cars are stuck together (coupled) and they are travelling at 3 m/s. (1) How fast was rail car A travelling before it collided with rail car B? (II) The two cars, stuck together, strike a spring buffer at the end of the track. If the spring buffer compresses by 50 cm to bring them to a halt, what is the spring constant of the buffer? (III) Before the collision, rail car A rolled from rest down 100 m of inclined track. What is the angle of the incline (measured from the horizontal)?

100 m Rail car A 5000 kg Rail car B 2000 kg Rail car A (5000 kg) collides with stationary rail car B (2000 kg). After the collision the two cars are stuck together (coupled) and they are travelling at 3 m/s. (1) How fast was rail car A travelling before it collided with rail car B? (II) The two cars, stuck together, strike a spring buffer at the end of the track. If the spring buffer compresses by 50 cm to bring them to a halt, what is the spring constant of the buffer? (III) Before the collision, rail car A rolled from rest down 100 m of inclined track. What is the angle of the incline (measured from the horizontal)?