I am a Junior in high school. My physics class is doing a workshop for the 5th and 6th graders at our school. We want to lift a kid in a chair with pulleys. I think we can use 4 fixed pulleys. My teacher told me to come back from spring break with a working model. I have not been able to come up with much besides some diagrams I got from Google and I can't understand them. Can someone give me some direction here?
What a hell is pulley? I look to my dictionary and even in my language don't understand this word.
I suggest this for your project, but you will have to make this a crash course, quickly?!
There is a handbook on pulleys and ropes, for maritime use, also one for shop mechanics.
You will have to go to the library or on line search to find this.
In this handbook, there is a complete rundown of how pulleys are made, what gauge and manufacture of ropes go through them and how the combinations are applied.
*Read this book thoroughly and if you can, either go to a local shop that has wooden pulleys of to a hardware store and get a double wheeled pulley and a length of nylon rope.
Read this book redundently, then with the materials you’ve purchased, practice the use of using pulley to rope combinations.
This is exactly what they use to do with naval recruits, as the nature of sailing involved pulleys and rope nomenclature, extensively.
SPECIAL NOTE: This is not an easy assignment. So you will need time. Go to your teacher and ask them to give you a special extended time to finish this project, if the time they are giving you to do this project, is too short.
If the time asked to finish the project is too unreasonable, then go to your parents and ask them to discuss the deadline asked with your teacher.
If its too unreasonable, then the parent can go to the school principle or superintendent, if there’s too much of a rush factor.
NOTE TO PARENT: Rope and pulley combinations in tandem, with any load placed on them, can be dangerous and can catch the person working with them.This is if they do not skill themselves completely in the action and use of rope pulley combinations.
So make sure if this project supports too much weight, or ask something difficult, that an adult is there to supervise?
Phys.org assumes no legal responsibilities in the lending of suggestions to any student or person asking for information.
There is a handbook on pulleys and ropes, for maritime use, also one for shop mechanics.
You will have to go to the library or on line search to find this.
In this handbook, there is a complete rundown of how pulleys are made, what gauge and manufacture of ropes go through them and how the combinations are applied.
*Read this book thoroughly and if you can, either go to a local shop that has wooden pulleys of to a hardware store and get a double wheeled pulley and a length of nylon rope.
Read this book redundently, then with the materials you’ve purchased, practice the use of using pulley to rope combinations.
This is exactly what they use to do with naval recruits, as the nature of sailing involved pulleys and rope nomenclature, extensively.
SPECIAL NOTE: This is not an easy assignment. So you will need time. Go to your teacher and ask them to give you a special extended time to finish this project, if the time they are giving you to do this project, is too short.
If the time asked to finish the project is too unreasonable, then go to your parents and ask them to discuss the deadline asked with your teacher.
If its too unreasonable, then the parent can go to the school principle or superintendent, if there’s too much of a rush factor.
NOTE TO PARENT: Rope and pulley combinations in tandem, with any load placed on them, can be dangerous and can catch the person working with them.This is if they do not skill themselves completely in the action and use of rope pulley combinations.
So make sure if this project supports too much weight, or ask something difficult, that an adult is there to supervise?
Phys.org assumes no legal responsibilities in the lending of suggestions to any student or person asking for information.
To the OP, Enthalpy's answer is the one to pay attention to. It should be obvious that DavidD and philip347 are dangerously thick-headed, to put it nicely... 
Need two puleyus like in tanks, one to motor and one to tree and then need very wide nematode and child then sit on it and puley ring him up onto you teach head 
QUOTE (Sapo's Feedback+)
DavidD Posted: Today at 1:08 PM
Negative "You have a dictionary? That's hilarious!"
Yes it is hilarious. laugh.gif And what means "hilariaus"?
What an idiot!
Negative "You have a dictionary?
That's hilarious!"Yes it is hilarious. laugh.gif And what means "hilariaus"?
What an idiot!
Simple answer.
1) Figure out what weight you can lift on your own easily.
2) Divide 150lb by that number
3) Round the answer up.
Then that is how many times your rope will need to go through a pulley.
For example, take it that you can lift 37.5lb on your own easily. You use 4 pulleys as shown below to lift the whole 150lb easily.
User posted image: http://upload.wikimedia.org/wikipedia/commons/1/17/Pulley3a.svg
Also, you can buy sets of pulleys that have wheels next to each other instead of separately therefore making the hook up to the chair easier than using two pulleys connected to balance the weight.
Hope that helps.
CKS
1) Figure out what weight you can lift on your own easily.
2) Divide 150lb by that number
3) Round the answer up.
Then that is how many times your rope will need to go through a pulley.
For example, take it that you can lift 37.5lb on your own easily. You use 4 pulleys as shown below to lift the whole 150lb easily.
User posted image: http://upload.wikimedia.org/wikipedia/commons/1/17/Pulley3a.svg
Also, you can buy sets of pulleys that have wheels next to each other instead of separately therefore making the hook up to the chair easier than using two pulleys connected to balance the weight.
Hope that helps.
CKS
Since you have 4 pulleys.
Attach 2 to the ceiling, the other 2 to the top of the chair.
Attach the rope to the ceiling.
Now run the rope through one of the chair pulleys, then through one of the ceiling pulleys.
If you were to pull on the free end of the role now, a pull of 25kg on the rope would now lift 50kg on the chair (chair weight included). You will need to pull the rope twice as far as the distance lifted though, kind of the point really.
Now run the remainder of the rope through the second chair pulley, then through the second ceiling pulley.
If you were to pull on the free end of the role now, a pull of 25kg on the rope would now lift 100kg on the chair (chair weight included). You will need to pull the rope four times as far as the distance lifted.
Attach 2 to the ceiling, the other 2 to the top of the chair.
Attach the rope to the ceiling.
Now run the rope through one of the chair pulleys, then through one of the ceiling pulleys.
If you were to pull on the free end of the role now, a pull of 25kg on the rope would now lift 50kg on the chair (chair weight included). You will need to pull the rope twice as far as the distance lifted though, kind of the point really.
Now run the remainder of the rope through the second chair pulley, then through the second ceiling pulley.
If you were to pull on the free end of the role now, a pull of 25kg on the rope would now lift 100kg on the chair (chair weight included). You will need to pull the rope four times as far as the distance lifted.
QUOTE (DavidD+Mar 28 2008, 11:39 AM)
What a hell is pulley? I look to my dictionary and even in my language don't understand this word.
@DavidD
Try a search of "Block and Tackle"
http://www.howstuffworks.com/pulley.htm
@snake20098,
If your going to be lifting a person I would do two things 1: engineer it to lift 300 lbs 2: build into the design an anti reversing device. you don't want to drop someone.
@DavidD
Try a search of "Block and Tackle"
http://www.howstuffworks.com/pulley.htm
@snake20098,
If your going to be lifting a person I would do two things 1: engineer it to lift 300 lbs 2: build into the design an anti reversing device. you don't want to drop someone.
PhysOrg scientific forums are totally dedicated to science, physics, and technology. Besides topical forums such as nanotechnology, quantum physics, silicon and III-V technology, applied physics, materials, space and others, you can also join our news and publications discussions. We also provide an off-topic forum category. If you need specific help on a scientific problem or have a question related to physics or technology, visit the PhysOrg Forums. Here you’ll find experts from various fields online every day.
To quit out of "lo-fi" mode and return to the regular forums, please click here.