A car weighing 50 tons moves at a speed of 9 km / h and meets a fixed platform weighing 30 tons

| September 17, 2021 | education

A car weighing 50 tons moves at a speed of 9 km / h and meets a fixed platform weighing 30 tons. Calculate the distance traveled by the car and the platform after coupling. Friction coefficient m = 0.05.

m1 = 50 t = 50,000 kg.
m2 = 30 t = 30,000 kg.
V = 9 km / h = 2.5 m / s.
V1 = 0 m / s.
k = 0.05.
g = 9.8 m / s ^ 2.
S -?
A = Ftr * S, the friction force performs the work of stopping the wagon with the platform.
Ftr = k * N, where k is the coefficient of friction, N is the force with which the platform with the car is pressed against the rails.
N = (m1 + m2) * g.
A = k * (m1 + m2) * g * S.
A = Ek, work is equal to the change in kinetic energy.
Ek = m1 * V ^ 2/2.
k * (m1 + m2) * g * S = m1 * V ^ 2/2.
S = m1 * V ^ 2/2 * k * (m1 + m2) * g.
S = 50,000 kg * (2.5 m / s) ^ 2/2 * 0.05 * (50,000 kg + 30,000 kg) * 9.8 m / s ^ 2 = 3.99 m.
Answer: S = 3.99 m.



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