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### Kurs: Fizyka w szkole średniej>Rozdział 5

Lekcja 5: Grawitacyjna energia potencjalna i siły zachowawcze

# Gravitational potential energy and conservative forces review

Review the key concepts and equations for gravitational potential energy, conservative forces, and nonconservative forces.

## Pojęcia kluczowe

Term (symbol)Meaning
Gravitational potential energy (${U}_{g}$)Energy due to position of an object in a gravitational field. SI unit is joule ($\text{J}$).
Conservative forceA force for which the work done by the force only depends on the initial and final positions and is independent of path taken. The net work is zero when the starting and ending positions are the same. An example is the force of gravity.
Nonconservative forceA force for which the work done depends on path taken. An example is the friction force.
Potential energy ($U$)Energy stored due to the position of an object.

## Równania

EquationSymbol breakdownMeaning in words
$\mathrm{\Delta }{U}_{g}=mg\mathrm{\Delta }y$$\mathrm{\Delta }{U}_{g}$ is change in gravitational potential energy, $m$ is mass, $g$ is the gravitational field strength, and $\mathrm{\Delta }y$ is change in height.The change in gravitational potential energy is directly proportional to mass, gravitational field strength, and change in height.

## Często spotykane błędy i nieporozumienia

1) Sometimes people are confused about how to measure height for a change in gravitational potential energy. Since the change in gravitational potential energy only depends on the change in height, the definition of where $y=0$ doesn’t matter. A common method is to choose the lowest location of the object as $y=0$.

## Dowiedz się więcej

For deeper explanations of conservative and nonconservative forces, see our video about conservative and nonconservative forces.
To check your understanding and work toward mastering these concepts, check out our exercise on calculating change in gravitational potential energy.

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