# Homework Help: Hair Dryer Project help!

1. Mar 6, 2010

### pulpfriction7

1. The problem statement, all variables and given/known data
Basically, using only a hair dryer as the source of energy, students need to create a machine that will lift a maximum amount of weight. Students get graded according to who can lift the heaviest weight. The record seems to be around 40kg...

2. Relevant equations
Can anyone inspire me a few ideas on how to achieve this??

3. The attempt at a solution
All I can think of is creating some sort of 'turbine' that would catch the hairdryer's air and rotate the turbine to lift the weight (creating mechanical advantage using pulleys or something like that).....

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EDIT - here are the complete rules:
the "Heavy-Weight Lifting Machine" - design&build a machine that lifts as much weight as possible up to a height of 110cm in any given time (meaning it could take a year to lift). The machine has to lift a min. of 260 grams. But the grade depends on the rank of the heaviness of the weights lifted. For example, if I lift 300g, and some other guy lifts 40kg, I will get a lower grade than he does.... pretty simple. :(

1. The hairdryer can be the only source of power. It can be the ONLY TYPE of power that supplies the power - so I CANT batteries using the hairdryer.... I also can't use the motor inside the hairdryer directly - like taking it out and doing something with it.
2. No counter weights - I can't drop a heavier weight to lift another object
3. ANY materials can be used to build the machine (metal, paper, foam, string, wire, etc), - BUT the total cost of the machine CANT exceed $25. BUT the items being used CAN be those that are recycled. For example, if I happen to have a "combustion engine" lying in my backyard, I could use it... Only I don't have a combustion engine lying in my backyard. 4. The machine can be set on a chair, floor, desk - anywhere. 5. The hairdryer can be moved around using my hands... THOSE are the ONLY rules there were given. No more, no less! Last edited: Mar 6, 2010 2. Mar 6, 2010 ### Jobrag I'd look at heating a fluid in a sealed system, possibly a bag of air with the weight on top then heat the bag, or a water filled cylinder with piston. For smaller weights but a better "wow" factor how about a hot air balloon? 3. Mar 6, 2010 ### pulpfriction7 Could a hairdryer heat the fluid hot enough to produce any kind of energy? I don't quite get what you are saying :( This is a high school project - I am hoping the ideas are not too complex for me :( Thank you anyways..! 4. Mar 6, 2010 ### Jobrag You don't say how far you are required to lift the weight, but the air in a sealed bag will expand as it is heated up. Remember your Boyles law P1*V1/T1 = P2*V2/T2 assuming that P will remain constant and that all the bag expansion will be upwards (V2>V1) If you start with the air in the bag at 20 Deg C and can increase the temperature by 10 Deg C the the upward expansion will be 3% of the original height. 5. Mar 6, 2010 ### pulpfriction7 My bad! Here are the requirements: 1. Lift up a mass of AT LEAST 260g 2. The machine must be able to lift at least a 110cm from the ground... Sorry about that..! 6. Mar 6, 2010 ### ephedyn The rules aren't clear enough... can you run the wire through the hairdryer, bypass the heater coil, go through another circuit then to a hydraulic fork lift? Is there a limitation to the additional items you can use to support your hairdryer? Blow someone's hair (for dramatic effect) as he lifts up the object? What's the shape of the object? How high must you lift the object? OK I had quite a laugh but anyway to be serious... personally I'd look into building a pressurized piston, with the hairdryer somehow inside the chamber. Look into (1) insulating the chamber from heat loss to the surroundings (2) minimizing the height of the pressurized air column which is to be heated (3) using a gas with high mol-to-volume ratio (4) designing the piston (how is it going to be sealed air-tight, how are you going to pre-pressurize the air inside and seal it before running the hair dryer - weld on a valve?) But clarifying the rules will help - I'm not sure - is a piston legal within the rules? How about chemicals? Is it fair to pressurize the piston before you start to use the hair dryer? I mean, if resources aren't a limit you could design something like a combustion engine and just have the hairdryer to somehow trigger an explosion, which is very possible, too. 7. Mar 6, 2010 ### pulpfriction7 I don't quite get the piston idea - could someone give me a visual aid? :( == Sorry... I might as well type up the whole paper. the "Heavy-Weight Lifting Machine" - design&build a machine that lifts as much weight as possible up to a height of 110cm in any given time (meaning it could take a year to lift). The machine has to lift a min. of 260 grams. But the grade depends on the rank of the heaviness of the weights lifted. For example, if I lift 300g, and some other guy lifts 40kg, I will get a lower grade than he does.... pretty simple. :( Additional Rules: 1. The hairdryer can be the only source of power. It can be the ONLY TYPE of power that supplies the power - so I CANT batteries using the hairdryer.... I also can't use the motor inside the hairdryer directly - like taking it out and doing something with it. 2. No counter weights - I can't drop a heavier weight to lift another object 3. ANY materials can be used to build the machine (metal, paper, foam, string, wire, etc), - BUT the total cost of the machine CANT exceed$25. BUT the items being used CAN be those that are recycled. For example, if I happen to have a "combustion engine" lying in my backyard, I could use it... Only I don't have a combustion engine lying in my backyard.
4. The machine can be set on a chair, floor, desk - anywhere.
5. The hairdryer can be moved around using my hands...

THOSE are the ONLY rules there were given. No more, no less!
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Last edited: Mar 6, 2010
8. Mar 6, 2010

### Jobrag

I've been doing some sums on this, if the hairdryer can produce a pressure of 5" water, (this is probably quite conservative) then if you can constrain this under an area of 1 square meter you should be able to lift over 130 Kg. I'd get two pieces of plywood and connect them with airtight (well fairly) material (salvaged carrier bags might do) connect the hairdryer up and blow air inbetween the two pieces of wood. This sounds like a job that will call for lots of duct tape!

9. Mar 6, 2010

### pulpfriction7

Wait - my knowledge in physics is very limited... (The teacher is honestly asking for too much.. I think... )

How would you measure if the "hairdryer can produce a pressure of 5" water?"
Could someone provide me with some sort of visual aid so that I can better understand this? Sorry :(

Thank you...

10. Mar 6, 2010

### Jobrag

To test the pressure capability of the hairdryer you will need a large plastic bag (rubbish sack) some clear plastic tube, a ruler and duct tape.
Tape the bag to the hairdryer so that the dryer will inflate the bag.
Fashion the tube into a U tube manometer (http://en.wikipedia.org/wiki/File:Manometer_(schematic_U-tube).svg) poke one end of the tube into the bag and tape in position, put enough water into the tube to come about halfway up each leg.
Make a small hole (about a pencil size) in another part of the bag.
Run the hairdryer and when the bag is inflated measure the difference in the hieght of the two legs, measurement in inches is the pressure that the hairdryer produces.

11. Mar 19, 2010

### pulpfriction7

Jobrag, thank you so much for the replies you've been giving.
I talked to a physics major friend of mine for literally a couple minutes, and he also thought the piston/chamber idea would be the best way to lift a heavy weight.
But he also said that it would be extremely hard to build such a machine. Plus, as of now, I really have no clue as to how I will build the actual machine...

Could you give any advice on this as well? thanks..!!

12. Mar 19, 2010

### Jobrag

Did you test the pressure capability of the hairdryer?