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 weight lifter on the barbell to that exerted by the barbell on the weight lifter. Is one force larger than the other or are they equal in magnitude to each other? Does this change during the times when the barbell slips downward? Explain.

A) When the barbell is at rest, both forces will be equal. Whereas, when the barbell is moved upwards, the force exerted on the barbell by the weight lifter will be greater than the gravitational force exerted on the weightlifter by the barbell.

B) When the barbell slips downward by the weight lifter, then we can say that the force due to gravity exerted by the barbell on the weight lifter is greater than the force exerted by the weight lifter on the barbell.

Explanation:

(A) When the barbell is at rest, both forces will be equal and opposite in direction. This is because the force exerted by the weight lifter on the barbell is equal to the force exerted by the barbell on the weight lifter.

Whereas, when the barbell is moved upward by the weight lifter, the force exerted on the barbell by the weight lifter will be greater than the gravitational force exerted on weightlifter by the barbell and thus direction is upward.

(B) When the barbell slips downward by the weight lifter, then we can say that the force due to gravity exerted by the barbell on the weight lifter is greater than the force exerted by the weight lifter on the barbell.

think about the oscillation of the toy shown in the video. when the toy is at the highest point of its motion, its velocity is zero and its acceleration is negative.

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