A car with a mass of m = 3 t, stops when braking for a time t = 8 s, having traveled equally slowly
| February 25, 2021 | education
A car with a mass of m = 3 t, stops when braking for a time t = 8 s, having traveled equally slowly a path S = 50 m. Find the initial vehicle speed and braking friction force.
1) S = (V ^ 2 – V0 ^ 2) / 2a, where S is the movement during braking (S = 50 m), V is the final speed (V = 0 m / s), V0 is the initial speed, and is the acceleration …
2) a = (V – V0) / t, where t is the braking time (t = 8 s).
a = – V0 / t.
3) S = – V0 ^ 2 / 2a = V0 ^ 2 * t / 2V0 = V0 * t / 2.
V0 = 2S / t = 2 * 50/8 = 12.5 m / s.
4) a = – V0 / t = -12.5 / 8 = -1.5625 m / s2.
5) Ftr = m * a, where m is the mass of the car (m = 3 t = 3000 kg).
Ftr = m * a = 3000 * 1.5625 = 4687.5 N.
Answer: V0 = 12.5 m / s, Ftr = 4687.5 N.
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