Analyzing Forces in a Platform and Pulley System

In summary, the conversation discusses a physics problem involving a girl standing on a platform and pulley system with different masses. The girl pulls up on the rope to accelerate upwards, and the questions raised include the tension of the rope, the normal force between the person and the platform, and the tension between the pulley and the platform. The conversation also includes a discussion on the net upward force that allows for the platform to move upwards.
  • #1
Paola Cavazos
1
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A girl stands on a platform and pulley system. The masses of the platform, girl and pulley are M, m and u respectively. The rope is mass-less. Let the girl pull up on the rope so that she accelerates a upwards. What is the tension of the rope? What is the normal force between the person and the platform? WHat is the tension connecting the pulley and the platform? I think that I should start from T - F = ma, but I really am kind of lost. I hope someone can help me find the accurate solution.

I uploaded an image of the exercise. Please help :)
 

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  • #2
Paola Cavazos said:
I think that I should start from T - F = ma
You should explain your thinking when asking for help. How did you get this equation? What is it saying?
 
  • #3
I have a small question Nathanael, I'm a bit confused with the problem too. Will the platform even move?? I'm sorry if this is a stupid question!
 
  • #4
Suraj M said:
I have a small question Nathanael, I'm a bit confused with the problem too. Will the platform even move?? I'm sorry if this is a stupid question!
It's not a stupid question. I can see how one would think the platform may not move, because the harder you pull up on the rope, the harder your feet push down on the platform. But the upwards force on the platform from pulling is greater than the increased force downward from pushing with your feet.
For the platform to move upwards (or more specifically, for it to accelerate upwards) there has to a net upwards force acting on the system. If the other end of the rope was attached to the platform, and the person was pulling up on it, then clearly it could not move upwards. But since the end of the rope is attached to the ceiling, an upwards external force acts on the platform (and person) allowing upwards acceleration.
P.S.
I like your avatar.
 
  • #5
I'm sorry but i still don't get how the upward force would be more than the downward. Could you explain?
 
  • #6
Suraj M said:
I'm sorry but i still don't get how the upward force would be more than the downward. Could you explain?
I purposely left the specifics of that detail out so as not to ruin it for the OP :) I will explain it to you in a private message.
 

1. How does a platform and pulley system work?

A platform and pulley system is a simple machine that uses a combination of wheels and ropes to lift or move heavy objects. The platform serves as the surface where the object is placed, while the pulley serves as a mechanism to distribute the weight across multiple ropes, making it easier to lift the object.

2. What are the advantages of using a platform and pulley system?

One major advantage of using a platform and pulley system is that it can reduce the amount of force needed to lift heavy objects. It also allows for more controlled and precise movements, making it useful in various industries such as construction and manufacturing.

3. How do I choose the right type of pulley for my platform and pulley system?

The type of pulley you need will depend on the specific application and the weight of the object you are trying to lift. Generally, single fixed pulleys are best for light loads, while double movable pulleys are better for heavier loads. It is important to consider the weight, size, and shape of the object when choosing the right pulley.

4. Can a platform and pulley system be used to lift objects vertically?

Yes, a platform and pulley system can be used to lift objects vertically. However, it is important to make sure that the ropes are properly aligned and that the pulleys are securely in place to ensure safe and efficient lifting.

5. Are there any safety precautions I should take when using a platform and pulley system?

Yes, it is important to follow safety precautions when using a platform and pulley system. This includes making sure that the ropes and pulleys are in good condition, using the appropriate type of pulley for the weight of the object, and ensuring that the platform is stable and can support the weight. It is also important to have proper training and supervision when using a platform and pulley system.

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