Question

A car is traveling at 20.0m/s. When the driver slams on the brake and bring it to a straight line stop in 4.2s. What is the magnitude of its average acceleration?

Answer 1

Given:

$v_0=20.0\;\rm m/s$

$v=0\;\rm m/s$

$\Delta t=4.2\:\rm s$

The magnitude of its average acceleration

$$a=\frac{\Delta v}{\Delta t}=\frac{20.0}{4.2}=4.8\:\rm m/s^2$$