The driver of a car moving at a speed of 54 km / h presses the brake pedal and stops after 5 seconds.
| September 2, 2021 | education
The driver of a car moving at a speed of 54 km / h presses the brake pedal and stops after 5 seconds. determine the acceleration of the vehicle. What will the vehicle speed be in 2.5 seconds after the start of braking.
V0 = 54 km / h = 15 m / s.
V = 0 m / s.
t = 5 s.
t1 = 2.5 s.
a -?
V1 -?
By definition, the acceleration of a body a shows how the body’s speed changes over time.
When braking, the acceleration of the car a is determined by the formula: a = (V0 – V) / t.
a = (15 m / s – 0 m / s) / 5 s = 3 m / s2.
a = (V0 – V1) / t1.
V0 – V1 = a * t1.
V1 = V0 – a * t1.
V1 = 15 m / s – 3 m / s2 * 2.5 s = 7.5 m / s.
Answer: the car decelerates with acceleration a = 3 m / s2, its speed after t1 = 2.5 s will be V1 = 7.5 m / s.
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