Unit 5
Energy.
Work, kinetic and potential energy on a roller coaster, the heat friction makes, power, and simple machines.
Before this unit
The unit, lesson by lesson
Lessons
4 lessons · 23 practice questions · about 2 hours
Work
A force that moves a body does work on it: the force times the distance moved along it. Forces at right angles to the motion do no work, friction does negative work, and the net work is the kinetic energy the body gains.
Kinetic and potential energy
A roller-coaster car without friction: its height is potential energy, its speed kinetic energy, and their sum is conserved. How fast is it at the bottom and at the top of the loop, and from what height does it make it round?
Heat and power
On a real track rolling resistance turns part of the energy into heat, but the total is conserved. How much heat is made, how much energy is left for motion, and what is the power of a motor that lifts the car?
Simple machines
A lever, pulleys and gears lift a heavy load with a small force. The mechanical advantage, the distance the effort moves, the work that does not change, and what efficiency is.