Initially, four identical uniform blocks, each of mass "m" and thickness "h", are spread on a table.How much work is done on the blocks in stacking them on top of one another?
Correct answer: D. 6mgh
- A. 2mgh
- B. 3mgh
- C. 4mgh
- D. 6mgh
Explanation
The work done on the blocks in stacking them on top of one another is equal to the force required to lift each block multiplied by the distance that each block is lifted.The force required to lift each block is equal to the weight of the block, which is mg.The distance that each block is lifted is equal to the thickness of the block, which is h. Hence, the answer is 6mgh according to following calculation:W = 0 + mgh + mg(2h) + mg(3h) = 6mghW = 0 + mgh + mg(2h) + mg(3h) = 6mgh
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About Work and Energy
Work transfers energy when a force causes displacement, while kinetic energy, gravitational potential energy and power describe motion, position and the rate of energy transfer. The work-energy theorem links net work with change in kinetic energy, and efficiency accounts for energy losses rather than treating them as energy destruction.
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