What is the likely damage to the equipment if a train is tripped while running at about 20 MPH?

When a train is tripped while running at approximately 20 MPH, the most likely consequence is the development of flat wheels. Tripping involves the train coming to an abrupt stop due to activation of the safety mechanism, which can cause the wheels to skid on the tracks, especially if the brakes are applied suddenly. This skidding can lead to flat spots forming on the wheels, referred to as flat wheels. These flat spots occur because the wheel continues to rotate while the locomotive and cars come to a halt, causing unnecessary wear on the wheel surface.

While other damages may occur in different circumstances, flat wheels are more directly associated with tripping incidents at that speed. For example, broken couplers, damaged air hoses, or cracked brake pads might relate to other issues such as collisions or excessive wear and tear over time rather than an abrupt stop caused by a tripping mechanism. Thus, flat wheels are the most immediate and likely damage resulting from a train tripping under these conditions.