Please help and provide a clear explanation regarding the Q.
A load of weight 2000N resting on the ground is lifted by a machine.
After lifting for 5 s, the load rises to a height of 3m and gains a speed of 4 m/s.
What is the average useful output power of the machine during the five seconds?
(The answer is 1.52kW.)
How can it work out?
Please help.
更新1:
I have another question regarding E&M, see if anyone can help, too. A metal rod with two ends A&B connected by a conducting wire is dropping vertically in a magnetic field. The direction of the field is pointing into the plane of the paper. What would be the induced current flow?
更新2:
┌────────┐ │X X X X X │ A└────────┘B X X X X X X X X X X Note that the line marked AB is the rod while the on the upper part is the wire using to connect A and B (The ans. is from B to A through the wire)
更新3:
Re: 胡雪八 I would like to know that why the USEFUL output energy would include the increase in KE of the load but not only the PE gain of the load? Please help! Thanks!