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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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