Work done on an object being lifted

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The discussion revolves around calculating the work done on a 72 kg astronaut being lifted 10 m by a helicopter with an acceleration of g/16. The initial attempt to calculate work using W=72*10*(9.8/16)*cos(0) is incorrect because it does not account for the net force acting on the astronaut. The upward force from the helicopter must exceed the gravitational force to achieve the given acceleration, indicating that the astronaut is not in free fall. Clarification on the forces involved is necessary for accurate calculations of work, kinetic energy, and speed. Understanding the relationship between the forces and acceleration is crucial for solving the problem correctly.
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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

 
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Dan Feerst said:
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! :smile:

The upward force from the helicopter isn't mass times g/16 … if it was, the astronaut would go down. :wink:
 
Wait. Are you saying the question is wrong?






Dan Feerst said:

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

 
No …
The acceleration of the astronaut is g/16

… what makes you think that all comes from the helicopter?
 
Not carefully reading the question apparently. :)
 

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