The driver of a car traveling at a speed of 20.0 m/s slams on the brakes and comes to a stop in 5.8 s. if we assume that the car's speed changed at a constant rate (constant net force), what was theaverage speed during this 5s interval?
average speed = m/s

10 m/s

Explanation:

u = 20 m/s

v = 0 m/s

t = 5.8 s

Let a be the acceleration and s be the distance traveled by the car in time t.

use first equation of motion

v = u + a t

0 = 20 + a x 5.8

a = -3.45 m/s^2

Use third equation of motion

s = 58 m

The average speed is defined as the ratio of distance traveled to the time taken.

thus, the average speed of the car is 10 m/s.  

the force on the thing and the distance the force moves the thing