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(a) The roof of a large arena, with a weight of 290 kN, is lifted by 30 cm so that it can be centered. How much work is done on the roof by the forces making the lift? (b) In 1960 a Tampa, Florida, mother reportedly raised one end of a car that had fallen onto her son when a jack failed. If her panic lift effectively raised 4000 N (about 1/4 of the car's weight) by 5 cm, how much work did her force do on the car?

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Answer:

87000 J ;

200 J

Explanation:

Workdone = mgh

Weight = mg = 290kN = 290 * 1000=290000 N

h = distance = 30 cm = 0.3 m

Workdone = 290000 * 0.3

Workdone = 87000 J

B.)

Workdone = Force * distance

Force = 4000 N

Distance, d = 5 cm = 0.05 m

Workdone by the woman, W = 4000N * 0.05m

W = 200Nm = 200 J

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