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| style="height:20px; width:400px; text-align:center;" |The equation for '''gravitational potential energy''' written in symbols.
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==Key Stage 4==
===Meaning===
The '''gravitational potential energy store''' is the [[Energy Store|energy stored]] in an [[object]] that is in a [[Gravitional Field|gravitional field]].
===About Gravitational Potential Energy===
: '''Gravitational Potential Energy''' is a [[Potential Energy|potential energy]] due to the position of a [[mass]] in a [[Gravitational Field|gravitational field]].
: The '''gravitational potential energy store''' of an [[object]] is related to three important factors:
*The [[mass]] - The greater the [[mass]] of an [[object]] the greater the '''gravitational potential energy'''.
*The [[Gravitational Field Strength|gravitational field strength]] - The greater the [[Gravitational Filed Strength|gravitational field strength]] the greater the '''gravitational potential energy'''.
*The [[height]] of the [[object]] - The greater the [[height]] of an [[object]] in a [[Gravitational Field|gravitational field]] the greater the '''gravitational potential energy'''.
===Equation===
''NB: You must memorise this equation!''
'' '''Gravitational Potential Energy''' = (Mass) x (gravitational field strength) x (change in height)''
<math>E_g = m g \Delta h</math>
Where:
E<sub>g</sub> = '''Gravitational Potential Energy''' stored.
m = The [[mass]] of the [[object]].
g = The [[Gravitational Field Strength|gravitational field strength]].
Δh = The change in [[height]] of the [[object]].
===Calculating Gravitational Potential Energy===
{| class="wikitable"
| style="height:20px; width:200px; text-align:center;" |A weight lifter lifts a 50kg [[mass]] a distance of 2.0m from the ground. Calculate the increase in '''gravitational potential energy''' of the [[mass]].
g on Earth is 9.8N/kg
| style="height:20px; width:200px; text-align:center;" |A pulley is used to lift a 12 tonne [[mass]] 0.80m above the ground. Calculate the change in energy in the gravitational potential store.
g on Earth is 9.8N/kg
Give your answer correct to two [[Significant Figures|significant figures]].
| style="height:20px; width:200px; text-align:center;" |During a rock slide a 320kg boulder falls from a [[height]] of 1450m to a height of 730m above sea level. Calculate the change in '''gravitational potential energy'''.
g on Earth is 9.8N/kg
Give your answer correct to two [[Significant Figures|significant figures]].
|-
| style="height:20px; width:200px; text-align:left;" |'''1. State the known quantities'''
m = 50kg
g = 9.8N/kg
Δh = 2.0m
| style="height:20px; width:200px; text-align:left;" |'''1. State the known quantities'''
m = 12tonne = 12,000kg
g = 9.8N/kg
Δh = 0.80m
| style="height:20px; width:200px; text-align:left;" |'''1. State the known quantities'''
m = 320kg
g = 9.8 N/kg
Δh = h<sub>2</sub> - h<sub>1</sub> = 1450 - 730 = 720m
|-
| style="height:20px; width:200px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers into the [[equation]] and [[Solve (Maths)|solve]].'''
<math>E_g = m g \Delta h</math>
<math>E_g = m \times g \times \Delta h</math>
<math>E_g = 50 \times 9.8 \times 2</math>
<math>E_g = 980J</math>
| style="height:20px; width:200px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers into the [[equation]] and [[Solve (Maths)|solve]].'''
<math>E_g = m g \Delta h</math>
<math>E_g = m \times g \times \Delta h</math>
<math>E_g = 0.80 \times 9.8 \times 12000</math>
<math>E_g = 94080J</math>
<math>E_g \approx 94000J</math>
| style="height:20px; width:200px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers into the [[equation]] and [[Solve (Maths)|solve]].'''
<math>E_g = m g \Delta h</math>
<math>E_g = m \times g \times \Delta h</math>
<math>E_g = 320 \times 9.8 \times 720</math>
<math>E_g = 2257920J</math>
<math>E_g \approx 2300000J</math>
|}