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Fizyka - program rozszerzony I

Lekcja 7: Moc

Podsumowanie wiadomości na temat mocy

Kluczowe pojęcia i definicje związane z pojęciem mocy. Różnica pomiędzy mocą i pracą.

Term (symbol)	Meaning
Power (P)	Rate at which work is done (or energy is transferred). SI units of start text, W, a, t, t, s, space, left parenthesis, W, right parenthesis, end text
Watt (start text, W, end text)	Power equivalent to transferring 1, start text, j, o, u, l, e, end text of energy per second. SI units of start fraction, start text, k, g, end text, dot, start text, m, end text, squared, divided by, start text, s, end text, cubed, end fraction

Equation	Symbols	Meaning in words
P, equals, start fraction, delta, E, divided by, delta, t, end fraction	P is power, delta, E is change in energy, and delta, t is change in time.	Power is the change in energy over the change in time.
P, equals, start fraction, W, divided by, delta, t, end fraction	W is work	Power is the work done over the change in time.

Some people confuse energy with power. Energy is a measurement of work done, while power is how energy changes with time.
Sometimes people forget that we can measure power by the work done by a force. We can substitute the work done by a force W, equals, F, delta, x, cosine, theta instead of change in energy into the equation

\begin{aligned}P&=\dfrac{\Delta E}{\Delta t}\\ \\ &=\dfrac{W}{\Delta t}\\ \\ &= \dfrac{F\Delta x\cos\theta}{\Delta t}\end{aligned}

If the force is along the direction of motion, then cosine, theta, equals, 1 and the equation can be re-written

P, equals, F, v, with, \bar, on top

where F is a constant force, and a change in distance over time is average velocity, v, with, \bar, on top.

For deeper explanations, see our video introducing power.

To check your understanding and work toward mastering these concepts, check out the exercise on relating power and energy.

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