physics: newton’s laws?

a weight lifter struggles but manages to keep a heavy barbell above his head. Occasionally he slips and the barbell starts to fall downward, but he always recovers. Compare the force exerted by the weightlifter on the barbell to that exerted by the barbell on the weighlifter. Is one force larger that the other or are they equal? Does this change during the times when the barbell slips downward?

A bowling ball rolls down the alley and hits a pin. Is one force larger than the other? Does this change any time during the collision?

A tennis player hits the ball with her racket. Is the force of the racket on the ball the same as the force of the ball on the racket? Does this every change during the collision?

2 Answers

  • These are all examples of Newton's third law:

    When he is holding the barbell steady the barbell exerts the same amount of force on the hands of the weightlifter as the hands of the weightlifter exerts on the barbell. If his hands exert less force than the weight then he slips and the barbell starts to fall downward, but the is still equal forces just less. When he recovers his hands exert more force, but so does the barbell.

    The force of the racket on the ball is the same as the force of the ball on the racket since it is again an action reaction force. If we are talking about two objects when one object exerts a force on another the other exerts an equal and opposite force on the first object.

    The same for the pins and ball

  • ????? You don't understand the real situation here... If God created the world, this world must remain factual for all of the people's understanding... Einstein, or Newton or any other philosopers and scientists, just DID THE PART of DISCOVERING the laws of physics.......... The real thought and the main purpose of discovering those physics laws, is to apply those laws for the sake of EASING our daily lives. The laws did not come first before God. How could you ask such irrelevant question..

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