Idea 3of 5Builds onBanked by heightCarried by motion
The total never changes
A pendulum swings away from your nose. Will it hit you?
Today you'll discover
- what a swing keeps the same from side to side
- the one rule above every store
- a shortcut that skips the whole path
Think firstReleased from your nose, the pendulum swings away
You release a pendulum from your nose and stand still. When it swings back, what happens?
Predict first, then press Next. Watch the total line while the bars trade.
A ledger with a small drawing of a pendulum and three bars. After a prediction, the frames advance: the height bar empties into the motion bar at the bottom of the swing, then refills on the far side a little short, with a small warmth bar appearing, while the total line stays put. The last step asks the speed at the bottom of a slide.
See the whole ideathe big idea and the key word, in one place
The big idea
Energy changes stores; the total never changes.
Compare themThe pendulum stops just short of your nose, never past it. Energy can move from height to motion and back, but it cannot grow on its own.
Key word
- conservation of energy
- the total energy of a closed system stays constant; energy changes form and store but is never created or destroyed
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?
- Use energy conservation to find a speed from a height, or a height from a speed, without kinematics.