A car moving at a speed of 50 km / h, stop on the way 120 meters. Find the braking time.
| August 19, 2021 | education
Initial data: V0 (vehicle speed to stop) = 50 km / h; S (braking distance of this vehicle) = 120 m; V (final speed) = 0 m / s.
SI system: V0 = 50 km / h = 50 * 1000/3600 m / s = 13.9 m / s.
1) Let’s define the acceleration:
S = (V ^ 2 – V0 ^ 2) / 2a = -V0 ^ 2 / 2a.
a = -V0 ^ 2 / 2S = -13.9 ^ 2 / (2 * 120) = -0.8 m / s ^ 2 (slow motion).
2) Find the braking time:
V = V0 + a * t and t = -V0 / a.
t = -13.9 / (-0.8) ≈ 17 s.
Answer: The vehicle braking time is 17 seconds.
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