The car moves at a speed of 54 km / h in how long it will stop if the braking distance is 15 m.
| April 12, 2021 | education
V0 = 54 km / h = 15 m / s.
V = 0 m / s.
S = 15 m.
t -?
We will assume that the car brakes with constant acceleration a.
The braking time t is expressed from the formula for acceleration: a = (V0 – V) / t. Since the car stopped V = 0 m / s, the formula will take the form: a = V0 / t.
t = V0 / a.
Let’s find the acceleration of the car a by the formula: a = (V0 ^ 2 – V ^ 2) / 2 * S.
Since V = 0 m / s, then a = V0 ^ 2/2 * S.
The formula for determining the braking time will take the form: t = V0 * 2 * S / V0 ^ 2 = 2 * S / V0.
t = 2 * 15 m / 15 m / s = 2 s.
Answer: the car will stop after time t = 2 s.
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