Work done on an object being lifted

[Dan Feerst]

Homework Statement

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?

Homework 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?

The Attempt at a Solution

 

[tiny-tim]

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?

Hi Dan!

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

 

[Dan Feerst]

Wait. Are you saying the question is wrong?

Homework Statement

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?

Homework 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?

The Attempt at a Solution

 

[tiny-tim]

No …

The acceleration of the astronaut is g/16

… what makes you think that all comes from the helicopter?

 

[Dan Feerst]

Not carefully reading the question apparently. :)