1. A sound engineer is setting up for an LMFAO concert. He uses 518 N of force t
ID: 1983940 • Letter: 1
Question
1. A sound engineer is setting up for an LMFAO concert. He uses 518 N of force to pull a large speaker 27 m. How much work has he done on the speaker?
2. The speaker has a mass of 62 kg. He has to raise the speaker 1.3 m. How much work does he have to do on the speaker?
3. It took him 4.9 s to lift the speaker the 1.3 m. How much power did he develop?
4. The third floor of a house is 8 m above street level. How much work is needed to move a 150 kg refrigerator to the third floor?
5. In 1985 in San Antonio, Texas, an entire hotel building was moved several blocks on thirty-six dollies. It took 284,200 N of force to move the building 352 m. How much work was done on the building?
6. How much work is done by a forklift raising a 583 kg box a distance of 1.2 m?
7. A champion weightlifter raises 240 kg a distance of 2.35 m. How much work is done lifting the weight?
8. How much work is done in pulling a box 2 m across a table with a force of 35 N?
9. A man lifts a 200 N water bucket at a constant speed from the bottom of a well. If he does 8 kJ of work in doing this, how deep is the well?
10. How much lifting work does a 60 kg student do as she climbs a flight of stairs 6 m high?
11. A student librarian picks up a 22 N book from the floor to a height of 1.25 m. He carries the book 37 m across library and places the book another 6.75 m above the ground. How much work was done on the book?
12. An electric motor lifts an elevator that weighs 1.2x104 N a distance of 9.0 m in 15 s. What is the power rating of the motor?
13. An engine moves a motorboat at a constant speed of 15 m/s. If the water offers a resistance of 6000 N, what is the power rating (in watts, in horsepower) of the engine?
14. How many steps on stairs (each step = 8 cm in height) does a 100 lb boy have to climb in 30 seconds to equal to power output of a 60 W light bulb?
Explanation / Answer
1. Work = force * distance = F x d = 518 N x 27 m = 13986 J
2. Weight of speaker = F =m * g = 62 kg x 9.8 m/s2= 617.4 N
Work to raise up = F x d = 617.4 N x 1.3 m = 802.62 J
3. Power = work /time = W/t = 802.62 J/4.9s = 163.8 Watt
4. Similar to (2)
Weight of Refrigerator= F =m * g = 150 kg x 9.8 m/s2=1470 N
Work to raise up = F x d = 1470 N x 8 m = 11760 J
5. Work = force * distance = F x d =284,200 N x 352 m = 100038400 J
6. Weight of box = F =m * g = 583 kg x 9.8 m/s2= 5713.4 N
Work to raise up = F x d = 5713.4 N x 1.2 m = 6856.08 J
7. Weight of weghit lifted = F =m * g = 240 kg x 9.8 m/s2= 2352 N
Work to raise up = F x d = 2352 N x 2.35 m = 5527.2 J
8. Work = force * distance = F x d = 35 N x 2 m = 70 J
9. Depth of well = d = W/F = (8000 J)/(200 N) = 40 m
10. Weight of girl = F =m * g = 60 kg x 9.8 m/s2= 588 N
Work to climb up = F x d = 588 N x 6 m = 3528 J
11. (a)Work1 = force * distance = F x d =22 N x 1.25 m = 27.5 J
(b)Work2 = force * distance = F x d =22 N x 37 m = 814 J
(c)Work3 = force * distance = F x d =22 N x 6.75 m = 148.5 J
Total Work= Work1 + Work2 + Work3 = 990 J
12. Power = work /time = W/t = (124.8 x 9) J/15s = 74.88 Watt
13.Power = work /time = F*v = 6000x15 = 90,000 Watt = 120.643 HP
14. Distance climbed = (Power x time )/Weight
weight = 45.36kg x 9.8 = 444.528 N
so
Distance climbed = (60W x 30 )/444.528 N= 4.05 m
Steps of stair = 4.05/0.08=51steps
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