The average acceleration is -5.21 m/s² and the stopping time is 5.2 sec.
Given,
Final velocity, v = 0
Initial velocity, u = 61 mph
mph to km/h
u = 97.6 km/h
Or, u = 27.11 m/s
Displacement, s = 231 feet
Or, s = 70.4 meter
By using the third equation of motion, we get
v² - u² = 2as
0 - (27.1)² = 2 × a × 70.4
Or, acceleration(a) = -5.21 m/s²
Now, by the first equation of motion,
v = u + at
Or, - u = at
-27.11 = -5.21 × t
Or, t = 27.11/5.21
t = 5.2 sec
The stopping time (t) is 5.2 sec
Hence, the average acceleration is -5.21 m/s², and the time is 5.2 sec.
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