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Edexcel A Level Physics:復(fù)習(xí)筆記2.19 Gravitational Potential Energy

Category: A-level課程, 教材筆記, 福利干貨 Date: 2022年10月8日上午10:59

Gravitational Potential Energy

Gravitational potential energy (usually written Ep, but sometimes GPE) is energy stored in a mass due to its position in a gravitational field
- If a mass is?lifted?up, it will?gain?Ep?(converted?from?other forms of energy)
- If a mass?falls, it will?lose?Ep?(and be converted?to?other forms of energy)
The equation for gravitational potential energy for energy changes in a?uniform gravitational field?is:

2-19-grav-energy-equation_edexcel-al-physics-rn

5.2.2-GPE-diagram

Gravitational potential energy (GPE): The energy an object has when lifted up

The potential energy on the Earth’s surface at ground level is taken to be equal to 0
This equation is only relevant for energy changes in a?uniform gravitational field?(such as near the Earth’s surface)

Derivation of GPE Equation

When a heavy object is lifted, work is done since the object is provided with an upward force against the downward force of gravity
- Therefore,?energy is transferred to the object
This equation can therefore be derived from the work done

2-19-grav-energy-equation-derivation_edexcel-al-physics-rn

Worked Example

To get to his apartment a man has to climb five flights of stairs.

The height of each flight is 3.7 m and the man has a mass of 74 kg.

What is the approximate gain in the man's gravitational potential energy during the climb?

A.? ? ?13 000 J? ? ? ? ? ? ???B.? ? ?2700 J? ? ? ? ? ? ? ?C.? ? ?1500 J? ? ? ? ? ? ? ?D.? ? ?12 500 J

WE-GPE-answer-image

Exam Tip

Gravitational potential energy questions often use falling objects, where you are expected to realise that, since energy is conserved, the gravitational potential energy?at the start?is equal to the kinetic energy?at the end.

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