Gravitational Potential Energy (Edexcel GCSE Physics: Combined Science)

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Gravitational Potential Energy

  • Energy in the gravitational store of an object is defined as:

The energy an object has due to its height in a gravitational field

  • This means:
    • If an object is lifted up, energy is transferred to its gravitational potential store 
    • If an object falls, energy will be transferred away from its gravitational potential store

gpe man, IGCSE & GCSE Physics revision notes

  • The change in the gravitational potential energy, ΔGPE of an object can be calculated using the equation:

ΔGPE = m × g × Δh

  • Where:
    • ΔGPE = change in gravitational potential energy, in joules (J)
    • m = mass, in kilograms (kg)
    • g = gravitational field strength in newtons per kilogram (N/kg)
    • Δh = change in vertical height in metres (m)

  • In Physics, Δ is the capital Greek letter 'delta' which stands for 'change in'

Gravitational Field Strength

  • The gravitational field strength (g) on the Earth is approximately 10 N/kg
  • The gravitational field strength on the surface of the Moon is less than on the Earth
    • This means it would be easier to lift a mass on the Moon than on the Earth

  • The gravitational field strength on the surface of the gas giants (eg. Jupiter and Saturn) is more than on the Earth
    • This means it would be harder to lift a mass on the gas giants than on the Earth

Gravitational field strength diagram, downloadable AS & A Level Physics revision notes

Some values for g on the different objects in the Solar System

Worked example

A man of mass 70 kg climbs a flight of stairs that is 3 m higher than the floor.

Gravitational field strength is approximately 10 N/kg.

Calculate the increase in energy in his gravitational potential store.

 

Step 1: List the known quantities

    • Mass of the man, m = 70 kg
    • Gravitational field strength, g = 10 N/kg
    • Change in height, Δh = 3 m

 

Step 2: Write down the equation for gravitational potential energy

increment G P E space equals space m space cross times space g space cross times space increment h

 

Step 3: Calculate the gravitational potential energy

increment G P E space equals space 70 space cross times space 10 space cross times space 3

increment G P E space equals space 2100 space straight J

 

Estimating Physical Quantities, downloadable AS & A Level Physics revision notes

Exam Tip

When doing calculations involving gravitational field strength, g, always use the value of 10 N/kg unless you are told otherwise in your exam question. You will be expected to remember the value of g for your exam!

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Leander

Author: Leander

Leander graduated with First-class honours in Science and Education from Sheffield Hallam University. She won the prestigious Lord Robert Winston Solomon Lipson Prize in recognition of her dedication to science and teaching excellence. After teaching and tutoring both science and maths students, Leander now brings this passion for helping young people reach their potential to her work at SME.