Simple Machines Scavenger Hunt

Nick Conrad

Spencer Milner

List of Simple Machines

• 1st class lever• 2nd class lever• 3rd class lever• Wheel and axle• Fixed Pulleys• Moveable Pulleys• Block and tackle• Inclined plane• Screw• Wedge• Gear

What is Mechanical Advantage?

• Mechanical Advantage (MA) is the advantage gained by the use of a mechanism in transmitting force.– A simple machine will either increase distance and

reduce force or increase force and reduce distance.

MA cont.

• IMA vs. AMA– IMA, or the ideal mechanical advantage, is the perfect world. There is

no friction loss and everything works at 100% efficiency.

1. DE is the effort distance

2. DR is the resistance distance

3. IMA = DE / DR

– AMA, or the actual mechanical advantage, is the cold reality. Friction is accounted for and nothing works at 100% efficiency.

1. FE is the effort force

2. FR is the resistance force

3. AMA = FR / FE

Dolly: 1st class lever and wheel and axle

• Let’s say you’re moving to a new house and you’ve got a ton of heavy boxes to move to the moving van. Now, since these boxes are fairly cumbersome and heavy you can only carry one at a time. With a dolly, not only can you carry more than one of these boxes at one time, but it also requires the user to apply less effort to move these boxes as a first class lever.

• 1st class lever IMA: 8.55:1• Wheel and axle IMA: 14.35:1• Multiplied IMA: 122.69:1

Quick Note: Gear ratio

• Gears don’t use MA the same way as the rest of the simple machines. Gears use what’s called GR, or gear ratio.

• There are four formulas, that are equal to one another, to find gear ratio, but you will at least need to be know one of these factors in order to find it, in other word, it must be given.

GR cont.

• GR consists of these formulas:– (“n” represents the # of teeth on a gear) n out/ n in– (“d” represents the diameter of the gear) d out/ d in– (this should be the Greek symbol, represents

angular velocity) W in/ W out– (funny looking “t” represents torque) t out/ t in

Gears on a bike: gears

• Bikes are great for getting around quicker than walking and can be a lot of fun, but try to imagine biking along rugged terrain, like mountain biking. It would be much more difficult to trudge through that terrain without gears. With gear sets, you don’t need to do that.

• Gear ratio: 0.428:1

Threads of a Light Bulb: screw

• You may have to screw in a light bulb for a while, but it takes a very small amount of force. You sacrifice distance for force just like any screw. Using threads gives you an advantage since it takes a lot of rotations to completely remove it from the socket.

• Light bulb IMA: 3.25(pi):1

Bottle Opener: 2nd class lever

• If you’ve ever tried to peel a bottle cap off of a bottle, you know how hard it is. With this bottle opener, you can use a second class lever to your advantage to pry it off.

• Bottle opener IMA: 5.44:1

Dagger: wedge

• Although this dagger has the potential to be a weapon, it can also be used as a convenient tool. It can be used to easily open mail such as letters or bills or it can be used to open boxes. These are pretty much the only uses I have personally for this item. It is not; however, ideal for cutting through thick materials.

• Dagger IMA:

Stapler: 3rd class lever

• We found that a stapler would classify as a third class lever. If the point of rotation was not spring loaded (so that it returned to the up position) the spot where the staples come out would be the resistance and the part above (where you push) would be the effort.

• Stapler IMA: .8:1