A weight lifter picks up a barbell and

1. lifts it chest high
2. holds it for 5 minutes
3. puts it down.

Estimate the amount of work the engine performed on a 1200 kg car as it accelerated at 1.2 m/s² over a 150 meter distance.

A real world roller-coaster released at point A and coasting without external power would traverse a track somewhat like the figure above. Friction is not negligible in the real world.
Does the roller-coaster have the same energy at points B and C? Is the total energy conserved during the coaster ride? Can you account for all the energy at any point on the track?

A gallon of gasoline contains about 1.3 x 10⁸ joules of energy. A 2000 kg car traveling at 20 m/s skids to a stop. Estimate how much gasoline it will take to bring the car back to the original speed. To complicate matters further, consider the fact that only about 15% of the energy extracted from gasoline actually propels the car. The rest gets exhausted as heat and unburnt fuel.