A vehicle A is stuck on the railroad tracks as a train B approaches with a speed of 120 km...

A vehicle A is stuck on the railroad tracks as a train B approaches with a speed of 120 km/h. As soon as the problem is detected, the train’s emergency brakes are activated, locking the wheels and causing the train’s wheels to slide relative to the tracks. If the coefficient of kinetic friction between the wheels and the track is 0.2, determine the minimum distance dmin at which the brakes must be applied to avoid a collision under the following circumstances:

(a) The train consists of just a 195,000 kg locomotive.

(b) The train consists of a 195,000 kg locomotive and a string of cars whose mass is 10 × 106 kg, all of which are able to apply brakes and lock their wheels.

(c) The train consists of a 195,000 kg locomotive and a string of cars whose mass is 10 × 106 kg, but only the locomotive is able to apply its brakes and lock its wheels.

Treat the train as a particle, and assume that the railroad tracks are rectilinear and horizontal.

Figure P4.10