Idea 2of 5Builds onBanked by heightHow fast, on the path
Carried by motion
The ball drops. Where does the banked energy go?
Today you'll discover
- what the height store turns into on the way down
- why the two bars always add to the same
- the name of the motion store
Think firstThe ball is let go. Halfway down
Halfway down, the ball has lost half its height. What happened to the 98 J it gave up?
Predict first, then press Next. Watch the two bars trade while the total line stays.
A ledger with a small drawing of a falling ball and three bars. After a prediction, the frames advance: the height bar shrinks while the motion bar grows by the same amount, the total line staying put, until the ball is just above the ground with all its energy in motion. The last step doubles a cart's speed and asks for the kinetic energy.
See the whole ideathe big idea and the key word, in one place
The big idea
Motion carries energy: kinetic energy, half m v squared.
Easy to get wrongDouble the speed does not double the kinetic energy. It quadruples it. Speed is squared in ½ m v².
Key word
- kinetic energy
- the energy an object has because it is moving: Ek = ½ m v²
About this modelThe bars move energy between stores; the total only changes when work is put in or taken out.
The bars move energy between stores; the total only changes when work is put in or taken out.
Ready to use it?
- Find the kinetic energy of a mass at a given speed, and say how it changes when the speed doubles.