Man pulling himself up at 0.2m/s^2

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To determine the force required for a man with a mass of 70 kg and a chair weighing 10 kg to accelerate upwards at 0.2 m/s², the relevant equation is F=ma. The total mass being lifted is 80 kg, and the gravitational force acting on it is 9.81 m/s². The correct calculation should consider the net acceleration, factoring in both gravity and the upward acceleration, leading to an effective gravitational force of 9.61 m/s². It is crucial to account for the pulley system involved and to draw a free body diagram to visualize the forces acting on the man and chair. Clarifying these details will help in accurately solving the problem.
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Homework Statement


A man with an 70kg mass, sits on chair of 10kg, and pulls himself upwards at a acceleration of 0.2m/s^2. What is the force needed to achieve this acceleration?


Homework Equations



F=ma

The Attempt at a Solution


F=(80)*(9.81+0.2)
F=(80)*(9.81-0.2)
Neither are giving a correct answer, please help!
 
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Well, he's not going to take the chair with him when he pulls himself up, I take it? So the mass is 70kg only.

Remember that the force of gravity is acting in the opposite direction to the direction the man is accelerating in. Taking the direction of acceleration due to gravity to be positive, and the direction of acceleration of the man to be negative (since it is against gravity) then the overall acceleration is 9.81 + (-0.2) = 9.61.
 
no, he is pulling himself and the chair upwards, he is on a pully system. sorry for not being clear. appreciate the quick response though!
 
thedarkone80 said:

Homework Statement


A man with an 70kg mass, sits on chair of 10kg, and pulls himself upwards at a acceleration of 0.2m/s^2. What is the force needed to achieve this acceleration?


Homework Equations



F=ma

The Attempt at a Solution


F=(80)*(9.81+0.2)
F=(80)*(9.81-0.2)
Neither are giving a correct answer, please help!
One of these last 2 equations is correct (do you know which?) There might be a problem with the number of significant figures you gave in your answer, or you could have done the arithmetic wrong. Since you didn't say what answer you got, it's hard to tell.
 
thedarkone80 said:
no, he is pulling himself and the chair upwards, he is on a pully system. sorry for not being clear. appreciate the quick response though!

Just read this more carefully, I didn't realize before there is a pulley system involved.

Have you drawn a free body diagram for the man+chair? In how many different places is a rope attached to them, including where the man is holding the rope to pull himself up?
 

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