Question

A race car is moving with a velocity of 144 kilometers/hour. The driver applies the brakes, and the car comes to a halt in 12.0 seconds. What is the average acceleration of the car during those 12.0 seconds? –12.0 meters/second2

Answer 1

First, we need to convert the units of the given velocity to m/sec
144 km/hr = (144 km / hr) x (1000 m / 1 km) x (1 hr / 3600 s) = 40 m/s

Now, to solve this question, we can use one of the equations of motion:
 a = (Vf - Vi) / t where:
a is the acceleration we are looking for
Vf is the final velocity of the car = 0 m/sec
Vi is the initial velocity of the car = 40 m/sec
t is the time taken = 12 seconds

Substitute with these givens in the above equation to get the acceleration as follows:
a = (0-40)/12 = -3.334 m/s^2