How much time does it take to lift the piano?

  • Thread starter BlackMamba
  • Start date
  • #1
187
0
Hello,

I thought I knew how to solve for this problem but alas I was wrong. I'm hoping someone will be able to point me in the right direction.

Here's the problem: A 1.40x10^2 kg piano is being lifted at a steady speed from ground level straight up to an apartment 18.0m above the ground. The crane that is doing the lifting produces a steady power of 4.00x10^2 W. How much time does it take to lift the piano?

So here's what I did:

The equation for power is P = W/t.

The equation for W (work done) is W = (Fcos0)s.

I have P (at least this is my thinking here). P is 4.00x10^2 and I would need to find W and then I could solve for t.

F = ma, however I don't know what my acceleration is. I calculated it with 9.80 but my answer was incorrect. So if all my original thinking in finding t is correct then all I really need help with is finding F.

Any help provided will be greatly appreciated.
 

Answers and Replies

  • #2
Pyrrhus
Homework Helper
2,178
1
Stunner, that does not equal work.

Conservation of Mechanical Energy
[tex] \Delta K + \Delta \Omega = 0 [/tex]

By the way, if the speed is steady(i suppose it means constant) what will be the change of kinetic energy?

You could apply (Conservative System Work)

[tex] W = -\Delta \Omega [/tex]

Alternatively,

Newton's 1st Law

[tex] \sum_{i=1}^{n} \vec{F}_{i} = 0 \rightarrow \vec{v} = constant [/tex]

You could use this to establish the force exerted to lift it is equal to the weight of the piano, in magnitude.
 

Related Threads on How much time does it take to lift the piano?

Replies
3
Views
12K
Replies
2
Views
2K
Replies
1
Views
2K
Replies
2
Views
6K
Replies
10
Views
2K
Replies
4
Views
3K
Replies
1
Views
698
Replies
2
Views
8K
Top