- The mechanic did 5406 Joules of work pushing the car.
That's the energy he put into the car. When he stops pushing, all the energy he put into the car is now the car's kinetic energy.
- Kinetic energy = (1/2) (mass) (speed²)
And there we have it
- The car's mass is 3,600 kg.
- Its speed is 'v' m/s .
- (1/2) (mass) (v²) = 5,406 Joules
(1/2) (3600 kg) (v²) = 5406 joules
1800 kg (v²) = 5406 joules
v² = (5406 joules) / (1800 kg)
v² = (5406/1800) (joules/kg)
= = = = = This section is just to work out the units of the answer:
- v² = (5406/1800) (Newton-meter/kg)
- v² = (5406/1800) (kg-m²/s² / kg)
= = = = =
v = √(5406/1800) m/s
v = 1.733 m/s
