# Physics

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Why can you exert a greater force on the pedals of a bike if you pull up on the handlebars?

Does it have anything to do with one of Newton's 3 laws? I'm not sure how to approach this question.

• Physics -

Stand on a scale and push on the ceiling :)

Third law. Force by man up on bars --> force down on man

Sum forces on the man who is not accelerating up or down

m g down + handlebar force down

force up on man = pedal force

net force = 0 so no change of momentum (F = m a = 0)
so

0 = m g down + handlebar force down - pedal up
so
pedal force UP on man = mg + handlebar force
so third law, equal and opposite force DOWN on pedal = m g + handlebar force

• Physics -

Thank you very much!

• Physics -

You are welcome.

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