Solving Pulley and Platform Homework w/ Acceleration

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The discussion revolves around solving a physics homework problem involving two construction workers using pulleys to raise themselves on a platform. Key points include the forces acting on both the workers and the platform, such as tension, normal force, and weight. Participants clarify the difference between the force applied by the workers and the tension in the ropes, emphasizing that the workers pull down on the rope, which creates an upward tension. The correct equations of motion are derived, leading to the conclusion that the acceleration of the workers can be expressed as (4f - 7mg) / 7m. The conversation highlights the importance of understanding the balance of forces and the role of mechanical advantage in the pulley system.
  • #31
lollikey said:
I got it ! the answer is (4f-7mg) / 7m
Good show.
 
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  • #32
Well, I can't understand why there are 4f and not 2f. I thought it was mechanical advantage but these pulleys are fixed to the ceiling, aren't they? I am obviously missing something.
 
  • #33
Poetria said:
Well, I can't understand why there are 4f and not 2f. I thought it was mechanical advantage but these pulleys are fixed to the ceiling, aren't they? I am obviously missing something.
Draw a line across just below the pulleys. How many ropes cross that line? What is the tension in each?
 
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  • #34
I see. There are four ropes and each of them has tension f.
 
  • #35
Poetria said:
I see. There are four ropes and each of them has tension f.
Right.
 
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  • #36
I got it. Many thanks. :)
 

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