1) A horizontal force of 120 Newtons is applied to a 15-kg crate to move it horizontally a distance of 6 meters across a concrete floor at a constant speed of 4 m/s. The task requires 1.5 seconds. The power rating for the person applying the force is approximately ___ W.
2) In a physcis lab, a 60-kg student runs up a 2-meter tall flight of stairs in 1.5 seconds. The student's power rating is approximately ___ W.
3) A 55-kg mountain clinber ascends(climbs) 15 meters up a steep cliff in 45 seconds. The power rating of the mountain climber is ___ W.
about physics (ENERGY)!!
2011-04-06 11:03 pm
回答 (2)
2011-04-07 4:58 am
✔ 最佳答案
1) Work Done = Fd (force x distance)= (120)(6)
= 720 J
Power = Energy / time
= 720 / 1.5
= 480 W
2) Potential Energy = mgh (mass x gravity x height)
= (60)(10)(2)
= 1200 J
Power = Energy / time
= 1200 / 1.5
= 800 W
3) Potential Energy = mgh (mass x gravity x height)
= (55)(10)(15)
= 8250 J
Power = Energy / time
= 8250 / 45
= 183.33 W
2011-04-06 21:02:44 補充：
技術問題,亂左少少。
不便之處,敬請原諒。
參考: me
2011-04-07 4:38 am
1. Displacement of the crate in 1.5 s = 4 x 1.5 m = 6 m
Work done = 120 x 6 J = 720 J
Power = 720/1.5 w = 480 w
2. Gain in potential energy = 60g x 2 J = 1200 J
Power = 1200/1.5 w = 800 w
[ g is the acceleration due to gravity, taken to be 10 m/s2]
3. Gain in potential energy = 55g x 15 J = 8250 J
Power = 8250/45 w = 183 w
Work done = 120 x 6 J = 720 J
Power = 720/1.5 w = 480 w
2. Gain in potential energy = 60g x 2 J = 1200 J
Power = 1200/1.5 w = 800 w
[ g is the acceleration due to gravity, taken to be 10 m/s2]
3. Gain in potential energy = 55g x 15 J = 8250 J
Power = 8250/45 w = 183 w
收錄日期: 2021-04-24 23:21:05
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20110406000051KK00489