Homework Help: Work done on an object being lifted

1. Oct 9, 2009

Dan Feerst

1. The problem statement, all variables and given/known data

A helicopter lifts a 72 kg astronaut 10 m vertically from the ocean by means of a cable. The acceleration of the astronaut is g/16. How much work is done on the astronaut by (a) the force from the helicopter and (b) the gravitational force on her? Just before she reaches the helicopter, what are her (c) kinetic energy and (d) speed?

2. Relevant equations

I have only attempted parts a and b so far, but I can't get a correct answer. I would assume, with a for example that
W=72*10*<9.8/16)*cos(0)=441
I have been trying the same tactic with b. what am I doing wrong?

3. The attempt at a solution

2. Oct 9, 2009

tiny-tim

Hi Dan!

The upward force from the helicopter isn't mass times g/16 … if it was, the astronaut would go down.

3. Oct 9, 2009

Dan Feerst

Wait. Are you saying the question is wrong?

4. Oct 9, 2009

tiny-tim

No …
… what makes you think that all comes from the helicopter?

5. Oct 9, 2009

Dan Feerst

Not carefully reading the question apparently. :)