A different type of pulley question -help

In summary, the conversation discusses a pulley question where a man in a box is pulling himself up at a constant velocity using a pulley system. The question is how to find the force needed for him to pull himself up, and what to do if he is accelerating upwards. The conversation also mentions the forces acting on the man and the box as a unit, and suggests using Newton's 2nd law. A helpful discussion and realization about the double force pulling up on the man is also mentioned.
  • #1
murphy
9
0
Okay, I have this crazy pulley question where a guy is sitting in a box that is attached to a pulley on the ceiling (the pulley system is ideal). He pulls himself up at a constant velocity -how do i find the force needed for him to pull himself up? (the rope goes around the pulley and back down to him- halfway around the pulley)
What about if he is accelerating upwards?
 
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  • #2
Identify all the forces acting on the "man + box" (treat them as a unit). Note that the man pulls down on one end of the rope, but both ends of the rope pull up on him. Apply Newton's 2nd law.

You may find this discussion helpful: https://www.physicsforums.com/showthread.php?t=46892
 
  • #3
thanks! I got it! - I didn't realize that the man had double force pulling up on him!
 

FAQ: A different type of pulley question -help

What is a pulley?

A pulley is a simple machine that consists of a wheel with a groove around its circumference, typically used to lift heavy objects by pulling a rope or cable through the groove.

How does a pulley work?

A pulley works by changing the direction of the force applied to an object. By using a rope or cable, the force applied downwards can be redirected upwards, making it easier to lift heavy objects.

What is the difference between a fixed pulley and a movable pulley?

A fixed pulley is attached to a stationary object, while a movable pulley is attached to the object being lifted. A fixed pulley only changes the direction of the force, while a movable pulley also provides a mechanical advantage by reducing the amount of force needed to lift the object.

How many pulleys do I need to lift an object?

The number of pulleys needed to lift an object depends on the weight of the object and the mechanical advantage desired. Generally, the more pulleys used, the easier it is to lift the object.

Can a pulley system be used to move objects horizontally?

Yes, a pulley system can be used to move objects horizontally by attaching the pulleys to a fixed point and using a rope or cable to pull the object along the ground.

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