2000-kg car decelerated from 10 m/s to 5 m/s. What is the work done on the car?

A 2000-kg car decelerated from 10 m/s to 5 m/s. What is the work done on the car?

Known:

Car's mass (m) = 2000 kg

Initial speed (vo) = 10 m/s

Final speed (vt) = 5 m/s

Wanted: net work

Solution:

Net work:

Wnet = ΔEK

Wnet = ½ m (vt2 - vo2)

Wnet = ½ (2000) (52 - 102)

Wnet = (1000) (25 - 100)

Wnet = (1000) (-75)

Wnet = - 75,000 Joule

The minus sign indicates that the direction of displacement is opposite with the direction of the net force.