The brakes on your automobile are capable of creating a deceleration of 4.7 m/s². If you are going 140 km/h and suddenly see a state trooper, what is the minimum time in which you can get your car under the 81 km/h speed limit?

2.4seconds

Explanation:

A body decelerating is known to have a negative acceleration.

Acceleration is the change in velocity of a body with respect to time. Mathematically,

Acceleration = change in velocity/time

Change in velocity = final velocity - initial velocity

Acceleration = final velocity (v) - initial velocity (u) /time taken (t)

This same formula will be used as the deceleration formula i.e

Deceleration = v-u/t

Given deceleration = -4.7m/s²(negative acceleration)

v = 81km/hr = (81000/3600)m/s = 22.5m/s

u = 140km/hr = (140,000/3600)m/s = 38.8m/s

Substituting the values into the deceleration formula we have;

-4.7 = 22.5-38.8/t

-4.7 = -11.3/t

-4.7t = -11.3

t = -11.3/-4.7

t = 2.4seconds

The minimum time in which you can get your car under the 81 km/h speed limit is 2.4seconds

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