Idea 4of 6Builds onPaying with a push
How fast you pay
Sprint the stairs or stroll them. What is different?
Today you'll discover
- what stays the same whether you sprint or stroll
- what changes
- the unit for how fast a bill is paid
Think firstThe same box, the same stairs, twice
Carry a box up the stairs in 10 s, then in 60 s. Which does more work?
Predict first, then drag the sliders. Watch the work bar stay while the power bar changes.
An energy ledger: a crate lifted by a winch, with bars for height and warmth and a hollow bar for the work put in. After a prediction, the work-and-power bench opens with sliders for force, distance and time, and two bars: the work done and the power. The last step asks the energy a motor transfers in twenty seconds.
See the whole ideathe big idea and the key word, in one place
The big idea
Power is work divided by time: how fast energy moves.
Easy to get wrongA bigger wattage is not more energy. It is energy faster. A 1000 W heater for one minute uses less than a 100 W bulb left on all night.
Key words
- power
- the rate of doing work or transferring energy: P = W ÷ t, in watts
- watt
- the unit of power, symbol W: one joule per second
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 power from work and time, or the energy from power and time.