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.

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