Question

9.A stock car is moving at 25.0 m/s when the driverapplies the brakes. If it stops in 3.00 s, what is itsaverage acceleration?

Answer 1

The average acceleration a of an object that changes its speed from v_0 to v_f during a time interval t is:

`a=(v_f-v_0)/(t)`

Since the car is initially moving at 25.0m/s and it stops in 3.00 seconds, then its final speed is 0m/s.

Replace v_f=0, v_0=25.0m/s and t=3.00s to find the average acceleration of the car:

`a=(0(m)/(s)-25.0(m)/(s))/(3.00s)=-8.333\ldots(m)/(s^2)`

Therefore, the average acceleration of the car when it stops from 25.0m/s in 3.00 seconds, is -8.33m/s^2.