A car whose initial speed is 40 m/s undergoes a constant acceleration of -5 m/s² when its brakes are applied.How much time does the car take to come to a stop? A)8 s B)16 s C)30 s D)200 s

Question

Quizplus · Accepted Answer

Using the equation,
v^2 = u^2 + 2as
where,
v = final velocity (0 m/s as the car comes to a stop)
u = initial velocity (40 m/s)
a = acceleration (-5 m/s^2)
s = distance traveled (unknown, but not needed for the time calculation)
Therefore, we have,
0^2 = 40^2 + 2(-5)s
0 = 1600 - 10s
10s = 1600
s = 160 m
Now, we can use the equation,
v = u + at
where,
v = final velocity (0 m/s)
u = initial velocity (40 m/s)
a = acceleration (-5 m/s^2)
t = time taken (unknown)
Therefore, we have,
0 = 40 - 5t
5t = 40
t = 8 s
Hence, the car takes 8 seconds to come to a stop.

A Car Whose Initial Speed Is 40 M/s Undergoes a Constant