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When the [[Force|forces]] acting in opposite directions are not [[equal]] in [[magnitude]].
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==Key Stage 3==
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===Meaning===
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'''Unbalanced Forces''' are [[Force]]s acting in opposite directions with different [[magnitude]]s.
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===About Unbalanced Forces===
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: When there are '''unbalanced forces''' on an [[object]] the [[object]] will [[accelerate]].
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{| class="wikitable"
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|-
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|[[File:UnbalancedForces1.png|center|150px]]
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|[[File:UnbalancedForces2.png|center|200px]]
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|[[File:UnbalancedForces3.png|center|200px]]
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|-
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| style="height:20px; width:200px; text-align:center;" |The 4[[Newton|N]] up and the 7[[Newton|N]] down mean the [[object]] will [[accelerate]] downwards due to a [[Resultant Force|resultant force]] of 3[[Newton|N]].
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| style="height:20px; width:200px; text-align:center;" |The 4[[Newton|N]] left and the 3[[Newton|N]] right mean the [[object]] will [[accelerate]] to the left due to a [[Resultant Force|resultant force]] of 1[[Newton|N]].
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| style="height:20px; width:200px; text-align:center;" |The 6[[Newton|N]] up is '''balanced''' by the 6[[Newton|N]] down but the 6[[Newton|N]] left and the 4[[Newton|N]] right mean the object will [[accelerate]] to the left due to a [[Resultant Force|resultant force]] of 2[[Newton|N]].
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|}
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==Key Stage 4==
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===Meaning===
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'''Unbalanced forces''' are [[force]] [[vector]]s which add together to make a (non-zero) [[Resultant Force|resultant force]].
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===About Balanced Forces===
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: When [[force]]s on an [[object]] are '''unbalanced''' it will [[accelerate]] (change speed or direction).
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: '''Unbalanced forces''' are related to [[Newton's First Law]] of motion:
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:: An [[object]] in motion will tend to stay in motion in a straight line and an [[object]] at [[rest]] will tend to stay at [[rest]] unless an [[Unbalanced Forces|unbalanced force]] acts upon it.
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: If the [[Resultant Force|resultant force]] on an [[object]] is not zero, then the [[force]]s are '''unbalanced'''.
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===Examples===
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{| class="wikitable"
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|-
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|[[File:ResultantForce1.png|center|200px]]
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|[[File:ResultantForce2.png|center|200px]]
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|[[File:ResultantForce3.png|center|200px]]
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|-
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| style="height:20px; width:200px; text-align:center;" |
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'''Choose which directions are positive.'''
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Up is positive.
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'''Calculate the [[Resultant Force]]'''
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There is 29N up and 37N down.
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F<sub>R</sub> = (+29N) + (-37N)
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F<sub>R</sub> = -8N upwards
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The [[force]]s are '''unbalanced'''.
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| style="height:20px; width:200px; text-align:center;" |
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'''Choose which directions are positive.'''
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Right is positive.
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'''Calculate the [[Resultant Force]]'''
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There is 114N right and 105N left.
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F<sub>R</sub> = (+114N) + (-105N)
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F<sub>R</sub> = 9N right
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The [[force]]s are '''unbalanced'''.
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| style="height:20px; width:200px; text-align:center;" |
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'''Choose which directions are positive.'''
 +
 
 +
Right is positive.
 +
Up is positive.
 +
 
 +
'''Calculate the [[Resultant Force]]'''
 +
 
 +
There is 38N up and 38N down.
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F<sub>R</sub> = (+38N) + (-38N)
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F<sub>R</sub> = 0N upwards
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The [[vertical]] [[force]]s are [[Balanced Forces|balanced]].
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'''Calculate the [[Resultant Force]]'''
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There is 50N right and 40N left.
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F<sub>R</sub> = (+50N) + (-40N)
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F<sub>R</sub> = 10N right
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The [[horizontal]] [[force]]s are '''unbalanced'''.
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|}
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===References===
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====AQA====
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:[https://www.amazon.co.uk/gp/product/019835939X/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=019835939X&linkCode=as2&tag=nrjc-21&linkId=57e96876985fc39b1a3d8a3e3dc238b6 ''Unbalanced forces, pages 118-119, GCSE Physics; Third Edition, Oxford University Press, AQA '']
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:[https://www.amazon.co.uk/gp/product/0008158770/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=0008158770&linkCode=as2&tag=nrjc-21&linkId=ec31595e720e1529e49876c3866fff6e ''Unbalanced forces, pages 146, 156, 180-1, GCSE Physics; Student Book, Collins, AQA '']
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====Edexcel====
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:[https://www.amazon.co.uk/gp/product/1292120223/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1292120223&linkCode=as2&tag=nrjc-21&linkId=068ecf40278c32406a7f1c6e66751417 ''Unbalanced forces, page 13, GCSE Physics, Pearson Edexcel '']

Latest revision as of 16:02, 29 November 2019

Contents

Key Stage 3

Meaning

Unbalanced Forces are Forces acting in opposite directions with different magnitudes.

About Unbalanced Forces

When there are unbalanced forces on an object the object will accelerate.
 
 
 
The 4N up and the 7N down mean the object will accelerate downwards due to a resultant force of 3N. The 4N left and the 3N right mean the object will accelerate to the left due to a resultant force of 1N. The 6N up is balanced by the 6N down but the 6N left and the 4N right mean the object will accelerate to the left due to a resultant force of 2N.

Key Stage 4

Meaning

Unbalanced forces are force vectors which add together to make a (non-zero) resultant force.

About Balanced Forces

When forces on an object are unbalanced it will accelerate (change speed or direction).
Unbalanced forces are related to Newton's First Law of motion:
An object in motion will tend to stay in motion in a straight line and an object at rest will tend to stay at rest unless an unbalanced force acts upon it.
If the resultant force on an object is not zero, then the forces are unbalanced.

Examples

 
 
 

Choose which directions are positive.

Up is positive.

Calculate the Resultant Force

There is 29N up and 37N down.

FR = (+29N) + (-37N)

FR = -8N upwards

The forces are unbalanced.

Choose which directions are positive.

Right is positive.

Calculate the Resultant Force

There is 114N right and 105N left.

FR = (+114N) + (-105N)

FR = 9N right

The forces are unbalanced.

Choose which directions are positive.

Right is positive. Up is positive.

Calculate the Resultant Force

There is 38N up and 38N down.

FR = (+38N) + (-38N)

FR = 0N upwards

The vertical forces are balanced.

Calculate the Resultant Force

There is 50N right and 40N left.

FR = (+50N) + (-40N)

FR = 10N right

The horizontal forces are unbalanced.

References

AQA

Unbalanced forces, pages 118-119, GCSE Physics; Third Edition, Oxford University Press, AQA
Unbalanced forces, pages 146, 156, 180-1, GCSE Physics; Student Book, Collins, AQA

Edexcel

Unbalanced forces, page 13, GCSE Physics, Pearson Edexcel
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