Physic -K.E. & P.E
2009-01-15 2:22 pm
A life accelerates upwards from rest to a speed of 5m/s in 1 second. What is the ratio at that time of its kinetic energy to the gravitational potential energy it has acquired?
回答 (1)
2009-01-15 3:17 pm
✔ 最佳答案
After 1 second, the speed of the lift is v = 5 ms-1.By h = (u + v)t / 2
Gain in height, h = (0 + 5)(1) / 2 = 2.5 m
So, the ratio of kinetic energy to the gravitational potential energy
= 1/2 mv2 : mgh
= 1/2 (5)2 : (10)(2.5)
= 1 : 2
參考: Myself~~~
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