The train, traveling at a speed of 10 m / s, was suddenly braked and stopped 30 s after the start of braking.

| January 12, 2021 | education

The train, traveling at a speed of 10 m / s, was suddenly braked and stopped 30 s after the start of braking. Determine the force with which the brake shoe was pressed against the wheel rim, if the train mass is 400 tons, and the total number of brake shoes is 180. The coefficients of friction of the wheels on the brake shoe are 0.20.

Data: V0 (speed before sudden braking) = 10 m / s; t (deceleration duration) = 30 s; m (train weight) = 400 t (400 * 10 ^ 3 kg); n (number of brake pads) = 180 pcs; μ (coefficient of friction of the wheels against the brake pad) = 0.2.
The force of pressing the shoe against the rim of the wheel (force of normal reaction) can be determined using Newton’s second law: m * a = m * (V0 / t) = Ftr. = μ * n * N, whence N = m * V0 / (t * μ * n).
Let’s perform the calculation: N = 400 * 10 ^ 3 * 10 / (30 * 0.2 * 180) ≈ 3704 N ≈ 3.7 kN.



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