Homework Answers
a) While lifting the weight and to keep it moving up with constant velocity he has apply the force of mg upwards . If the displacement is d in the upwards direction then the work done by him is + mgd
b) while lowering the weight the gravitational force will try to accelerate the weight downwards , in order to keep it moving downwards with a constant speed he has to apply the mg force in the upwards direction while the displacement is happening in the downwards direction . Hence the work done by him will be - mgd.
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The weight is raised and lowered at a constant velocity. Determine the work done on the...
A weight lifter is bench-pressing a barbell whose weight is 710 N. He raises the barbell...
A weight lifter is bench-pressing a barbell whose weight is 710 N. He raises the barbell a vertical distance of 0.65 m, and then lowers it back to its original position next to his chest. Assume the weight is raised and lowered at a constant velocity, and that “up” is the positive direction. Determine the work done on the barbell (a) While the barbell is being raised (b) While the barbell is being lowered
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A 50 kg rock is raised 20 m at a constant velocity by a crane. The...
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In exercising, a weight lifter loses 0.219 kg of water through evaporation, the heat required to...
In exercising, a weight lifter loses 0.219 kg of water through evaporation, the heat required to evaporate the water coming from the weight lifter's body. The work done in lifting weights is 1.58 x 105 J. (a) Assuming that the latent heat of vaporization of perspiration is 2.42 x 106 J/kg, find the change in the internal energy of the weight lifter. (b)Determine the minimum number of nutritional Calories of food that must be consumed to replace the loss of...
In exercising, a weight lifter loses 0.174 kg of water through evaporation, the heat required to...
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In exercising, a weight lifter loses 0.124 kg of water through evaporation, the heat required to...
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A weightlifter stands up at constant speed from a squatting position while holding a heavy barbell...
A weightlifter stands up at constant speed from a squatting
position while holding a heavy barbell across his shoulders.
a) Draw a free-body diagram for the barbell.
Draw the vectors starting at the black dots. The location and
orientation of the vectors will be graded. The length of the
vectors will not be graded.
B) Draw a free-body diagram for the weight
lifter. Draw the vectors starting at the black dots. The location
and orientation of the vectors will be...
A weightlifter stands up at constant speed from a squatting
position while holding a heavy barbell across his shoulders.
a) Draw a free-body diagram for the barbell.
Draw the vectors starting at the black dots. The location and
orientation of the vectors will be graded. The length of the
vectors will not be graded.
B) Draw a free-body diagram for the weight
lifter. Draw the vectors starting at the black dots. The location
and orientation of the vectors will be...
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