Physics AS question Watch

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slop8
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#1
Report Thread starter 14 years ago
#1
Hello, would anyone be able to indicate a suitable answer for this question:

'Newtons 3rd law is sometimes stated in the form: "To every action there is an equal and opposite reaction". A student argues that, in that case, the resultant force on an object must always be zero and so it can never be moved. Exlpain what is wrong with the students arguement.'

Thank you very much. Any help appreciated.
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john !!
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#2
Report 14 years ago
#2
The student is applying the 3rd law pair to the same object as the original force.
In fact, the 3rd law pair applies to the object causing the original force on the first object.
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slop8
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#3
Report Thread starter 14 years ago
#3
(Original post by mik1w)
The student is applying the 3rd law pair to the same object as the original force.
In fact, the 3rd law pair applies to the object causing the original force on the first object.
thanks for the reply though could you give some more detail? doesnt the original force increase when a greater force is aplied??
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slop8
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#4
Report Thread starter 14 years ago
#4
anyone?
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lukeD
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#5
Report 14 years ago
#5
imagine kicking a football...

your foot exerts a force on the ball
and, according to newtons third law, the ball exerts a force on your foot

the two forces do not cancel out to give zero because one of the forces is acting on the ball and the other one is acting on your foot.

therefore the resultant force on the ball is NOT zero and it can accelerate.
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