A car weighing 14 tons, moving away, travels the first 50 m in 10 s. Find the amount

A car weighing 14 tons, moving away, travels the first 50 m in 10 s. Find the amount of thrust if the resistance is 0.05.

m = 14 t = 14000 kg.

V0 = 0 m / s.

S = 50 m.

t = 10 s.

g = 10 m / s2.

μ = 0.05.

Fт -?

Let us write 2 Newton’s law in vector form for a car when it moves from a place: m * a = Fт + Fтр + m * g + N.

ОХ: m * a = Fт – Fтр.

DT: 0 = -m * g + N.

Ft = m * a + Ftr.

N = m * g.

We see that the traction force Ft is used to impart acceleration to the car and overcome the friction force.

Ftr = μ * N = μ * m * g.

Fт = m * a + μ * m * g = m * (a + μ * g).

We express the acceleration of the car a from the formula: S = V0 * t + a * t ^ 2/2 = a * t ^ 2/2.

a = 2 * S / t ^ 2.

a = 2 * 50 m / (10 s) ^ 2 = 1 m / s2.

Ft = 14000 kg * (1 m / s2 + 0.05 * 10 m / s2) = 21000 N.

Answer: when moving from a standstill, the car develops a traction force Ft = 21000 N.