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    Motion in one and two dimensions ondivino

    How to answer this?

    Abraham is sitting on a chair. He correctly tells his friend Bashir that the chair is exerting an upward force on him equal to his weight force. Abraham then claims that the two forces are equal because they are two parts of an action-reaction pair.

    Is he correct? Explain your answer.


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      He is incorrect (with his second claim). The 2 forces are equal because the net force on Abraham is zero (which is because he is stationary and therefore has no acceleration.) Normal force and weight are NEVER an action-reaction pair. They are separate forces; each force has its own "reaction". The reaction to the weight experienced by Abraham is the gravitational pulling force by Abraham on the Earth. The reaction to the normal force on Abraham by the chair is the normal force applied by Abraham to the chair.

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