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.