A bus weighing 4 tons starts to move and on the way of 100 m acquires a speed of 20 m / s.

| May 21, 2021 | education

A bus weighing 4 tons starts to move and on the way of 100 m acquires a speed of 20 m / s. Determine the traction force and the work of the friction force if the coefficient of friction is 0.4 Initial speed is zero.

Data: m is the mass of the bus (m = 4 t = 4 * 10 ^ 3 kg); S – distance traveled (S = 100 m); V is the acquired speed (V = 20 m / s); μ – coefficient of friction (μ = 0.4); V0 – initial speed (V0 = 0 m / s).

Const: q – acceleration due to gravity (q ≈ 10 m / s2).

1) Traction force: m * a = Ft – Ftr, whence we express: Ft = m * a + Ftr = m * V2 / 2S + μ * m * g = 4 * 10 ^ 3 * 202 / (2 * 100) + 0.4 * 4 * 10 ^ 3 * 10 = 24 kN.

2) Work performed by friction force: Atr = -Ftr * S = -μ * m * g * S = -0.4 * 4 * 10 ^ 3 * 10 * 100 = -1.6 MJ.

Answer: The traction force is 24 kN, the frictional force did the work at -1.6 MJ.



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