What is the required force to lift oneself using movable pulleys?

In summary, the question asks to determine the force needed to lift a man and platform weighing 780 N with a frictionless pulley. The solution is found by setting the tension in the rope equal to the weight of the man and platform, resulting in a force of 780 N.
  • #1
xX1SHOt
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1. Homework Statement

In the figure below, the man and the platform together weigh 780 N. The pulley can be modeled as frictionless. Determine how hard the man has to pull on the rope to lift himself steadily upward above the ground.

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____________N



2. Homework Equations

I didn't use any until it said i was wrong but here is what it would be:

mg = T(1) + T(2)
T(1) = T(2)



3. The Attempt at a Solution

mg = 780 N = 2*T(1)

780 N / 2 = T(1)

390 N = T(1)

I first entered 390 and it was wrong, then I tried 391 to steadily move it upward. Both were wrong. Any help?
 

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  • #2
cant anyone help
 
  • #3
I believe the answer is simply T = 780 N.

T - mg = m(0)
T = mg = 780 N

They didn't give you any value for the acceleration which if they did would've changed alot.
 
  • #4
nevermind i figured it out, thanks
 

FAQ: What is the required force to lift oneself using movable pulleys?

How does a movable pulley affect the amount of force needed to lift an object?

A movable pulley reduces the amount of force needed to lift an object by half. This is because the weight of the object is distributed between the two sides of the pulley, with half of the weight being supported by the pulley itself.

What is the mechanical advantage of a movable pulley?

The mechanical advantage of a movable pulley is 2. This means that the force applied to the rope or cable is multiplied by 2, resulting in a greater force being exerted on the load.

Can multiple movable pulleys be used together to further decrease the force needed to lift an object?

Yes, multiple movable pulleys can be used together to further decrease the force needed to lift an object. Each additional pulley will divide the necessary force by the number of pulleys, resulting in a greater mechanical advantage.

How does the direction of the force change when using a movable pulley?

The direction of the force needed to lift the object changes when using a movable pulley. Instead of pulling down on the rope or cable, the force is now directed upwards. This is because the pulley is changing the direction of the force.

Are there any limitations to using movable pulleys?

One limitation of using movable pulleys is that they can only decrease the amount of force needed to lift an object, they cannot increase it. Also, the mechanical advantage is limited by the number of pulleys used and the friction within the pulley system.

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