[1] A person holds a heavy object in the air, and thus the person is doing work.

Question

[1] A person holds a heavy object in the air, and thus the person is doing work. This statement is: correct, incorrect. [2] A box begins to move, which means it has kinetic energy. This statement is: correct, incorrect. 18] When two surfaces are rubbed together (like one hand against the other hand), the work done by the frictional forces is converted without loss into heat absorbed by the two surfaces. This statement is: correct, incorrect. (4] Person A lifts a 20 N object upward through a distance of 1 m in a time of 2 s person B lifts a 10 N object upward through a distance of 1 m in a time of 2 s As a result, person A: does more work and produces more power, does more work but produces same power, does same work but produces more power, does same work but produces less power, does less work while producing more power [5] Two people climb the same flight of stairs of height 5 m. Both have a mass of 75 kg. Person A climbs the stairs in a time of 10 s, while person B climbs the stairs in 15 s. As a result, person A: does more work and produces more power, does more work but produces same power, does same work but produces more power, does same work but produces less power, does less work while producing more power. [6] Even without frictional effects, a person will be unable to hear a sound when too far from the source of the sound. This is because as the sound travels out in all directions it loses: energy, intensity, power, work.

Explanation / Answer

Q1. Incorrect ( It is so because work is said to be done when there is displacement in direction of force applied.Here no displacement so no work is done.

Q2.Correct( box is moving means it has velocity hence it has kinetic energy)

Q3. Incorrect ( This is so because when two bodies are rubbed work done by friction force is converted into heat energy which is partly absorbed by two mating surface and parlty is lost to environment if it not insulated properly.)

Q4.A does more work and produces more power in comparision to B beacuse A does 20Nm work ( force x displacement) and produces10 W power (work/time) whereas B does 10Nm work and produces 5 W power.

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