The driver of the car, moving at a speed of 72 km / h, began to brake.
| August 17, 2021 | education
The driver of the car, moving at a speed of 72 km / h, began to brake. How far the car has traveled to a complete stop if its braking acceleration is 4 m / s
V0 = 72 km / h = 20 m / s.
V = 0 m / s.
a = 4 m / s2.
S -?
When braking with constant acceleration, the path S traveled by the car can be expressed by the formula: S = V0 * t – a * t ^ 2/2, where V0 is the speed of the car at the beginning of braking, t is the braking time, and is the acceleration during braking.
The braking time t is expressed from the formula for acceleration: a = (V0 – V) / t.
t = (V0 – V) / a.
t = (20 m / s – 0 m / s) / 4 m / s2 = 5 s.
S = 20 m / s * 5 s – 4 m / s2 * (5 s) ^ 2/2 = 50 m.
Answer: to a complete stop, the car covered the distance S = 50 m.
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