Answer:
Explanation:
You want to know the acceleration and stopping time of a car slowing from 120 km/s to rest in 160 m.
The relation between stopping distance, velocity, and time is ...
d = (1/2)vt
t = 2d/v = (2)(0.160 km)/(120 km/s) = 0.32/120 s = 0.00266... s
The stopping time is 2 2/3 milliseconds.
The acceleration is the change in velocity divided by the corresponding time:
a = ∆v/t = (-120 km/s)/(8/3 ms) = -360/.008 km/s² = -45000 km/s²
The acceleration is -45000 km/s².
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Additional comment
At 120 km/s, the car is traveling about 3000 times as fast as any car we usually see on the road. If that speed is supposed to be 120 km/h, the stopping time would be about 9.6 seconds, and the deceleration would be about 3.4722... m/s², or about -0.354 g. That's much closer to what we expect of an actual car.
