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Lekcja 8: Moc

# Podsumowanie wiadomości na temat mocy

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

## Pojęcia kluczowe

Term (symbol)Meaning
Power ($P$)Rate at which work is done (or energy is transferred). SI units of $\text{Watts (W)}$
Watt ($\text{W}$)Power equivalent to transferring $1\phantom{\rule{0.167em}{0ex}}\text{joule}$ of energy per second. SI units of $\frac{\text{kg}\cdot {\text{m}}^{2}}{{\text{s}}^{3}}$

## Równania

EquationSymbolsMeaning in words
$P=\frac{\mathrm{\Delta }E}{\mathrm{\Delta }t}$$P$ is power, $\mathrm{\Delta }E$ is change in energy, and $\mathrm{\Delta }t$ is change in time.Power is the change in energy over the change in time.
$P=\frac{W}{\mathrm{\Delta }t}$$W$ is workPower is the work done over the change in time.

## Często spotykane błędy i nieporozumienia

1. Some people confuse energy with power. Energy is a measurement of work done, while power is how energy changes with time.
2. Sometimes people forget that we can measure power by the work done by a force. We can substitute the work done by a force $W=F\mathrm{\Delta }x\mathrm{cos}\theta$ instead of change in energy into the equation
$\begin{array}{rl}P& =\frac{\mathrm{\Delta }E}{\mathrm{\Delta }t}\\ \\ & =\frac{W}{\mathrm{\Delta }t}\\ \\ & =\frac{F\mathrm{\Delta }x\mathrm{cos}\theta }{\mathrm{\Delta }t}\end{array}$
If the force is along the direction of motion, then $\mathrm{cos}\theta =1$ and the equation can be re-written
$P=F\overline{v}$
where $F$ is a constant force, and a change in distance over time is average velocity, $\overline{v}$.

## Dowiedz się więcej

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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