Question

A car, initially traveling at 7.4 miles per hour , comes to rest in 9.7s. What was its acceleration in this time?

Answer 1

The acceleration of an object is the quotient between the change in the velocity of the object over the time that it takes for the object to change its velocity:

`a=(\Delta v)/(\Delta t)=(v_f-v_0)/(\Delta t)`

Since the car comes to rest, the final velocity of the car is 0. Then, replace v_0=7.4mi/h, v_f=0 and Δt=9.7s to find the acceleration of the car:

`a=(0-7.4(mi)/(h))/(9.7s)=-0.7628865979\ldots(((mi)/(h)))/(s)\approx-0.76(((mi)/(h)))/(s)`

Therefore, the acceleration of the car during that time, was -0.76 miles per hour per second.