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

  • Thread starter Thread starter xX1SHOt
  • Start date Start date
  • Tags Tags
    Force Pulleys
AI Thread Summary
To determine the force required for a man weighing 780 N to lift himself using movable pulleys, the tension in the rope must equal half of his weight due to the mechanics of the pulley system. The initial calculation suggested that pulling with a force of 390 N would suffice, but this was incorrect. The correct approach indicates that the total tension must equal the man's weight, leading to the conclusion that he needs to exert a force of 780 N to lift himself steadily. The absence of an acceleration value in the problem complicates the calculations, but ultimately, the solution was found. Understanding the dynamics of tension in pulley systems is crucial for solving such problems effectively.
xX1SHOt
Messages
18
Reaction score
0
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.

p4-33.gif


____________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?
 

Attachments

  • p4-33.gif
    p4-33.gif
    11.7 KB · Views: 747
  • p4-33.gif
    p4-33.gif
    11.7 KB · Views: 501
  • p4-33.gif
    p4-33.gif
    11.7 KB · Views: 498
  • p4-33.gif
    p4-33.gif
    11.7 KB · Views: 481
Physics news on Phys.org
cant anyone help
 
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.
 
nevermind i figured it out, thanks
 

Thread 'Rolling without slipping on a curved surface'

Kindly see the attached pdf. My attempt to solve it, is in it. I'm wondering if my solution is right. My idea is this: At any point of time, the ball may be assumed to be at an incline which is at an angle of θ(kindly see both the pics in the pdf file). The value of θ will continuously change and so will the value of friction. I'm not able to figure out, why my solution is wrong, if it is wrong .
View full post »

Thread 'Struggling to understand the concept of this question (ice cube in water optics question)'

TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
View full post »

Similar threads

Problem with pulleys - two fixed and one movable
Replies
22
Views
380
Time period of SHM & Energy conservation in pulley-spring-block system
Replies
24
Views
3K
Torque of Pulley with Two Masses2
Replies
6
Views
2K
How Does Nick's Acceleration Change When His Friend Pulls the Rope?
Replies
6
Views
4K
Person pulling themselves up a double pulley
Replies
19
Views
5K
Force applied on the pulley of a system
Replies
8
Views
3K
What is the acceleration of two masses on pulleys with constant tension?
Replies
10
Views
1K
Ball suspended by a pulley: oscillation
Replies
2
Views
1K
How do masses and pulleys behave in a balanced system with different weights?
Replies
10
Views
1K
Calculating the force for a differential pulley
Replies
20
Views
4K

Hot Threads

Recent Insights

Back
Top