Professor Herbert Johnson's Science
"I didn't fail the test, I just found 100 ways to do it wrong." -Benjamin Franklin
Simple MACHINES
This week in Professor Herbert's laboratory, the subject is simple machines. There are many different types of simple machines, they can be, levers, ramps, screws, wheels, gears or even pulleys.
To do anything at all—to lift a box, to push a car, to get out of bed, to jump in the air, to brush your teeth—you need to use a pushing or pulling action called a force.
When you think of the word machine, a big tractor probably pops into your thoughts, but a machine, no matter how simple it may be, is just something that makes a force bigger.
For more information on simple machines check out these websites, they've got games, facts and so much more!
http://pbskids.org/zoom/games/goldburgertogo/
http://www.neok12.com/Simple-Machines.htm
Simple Machines...
About Us
Professor Herbert Johnson's Science is abundantly idiosyncratic, because it's a great way to learn more about the science of our world!
This site is full of fun and whacky facts about simple machines!
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Wheels and Gears
WHEELS
Wheels and axles are simple machines and usually counted as one. A door knob is a wheel and axle. The inmost wheel is called the axle. When a door is open, the effort you apply to the wheel makes the axle pull the load and open the door. The fulcrum is in the very centre of the door knob.
A door knob would be a force multiplier because it only takes a little bit of effort to move a big load. Sort of like a gate, if the door knob is too close to the hinge it would be harder to open, same goes for a gate, if you try and push it really close to the hinge, it will be really hard to open. A wheel and axle machine can also be a speed multiplier, like a fan, it's a wheel and axle machine as well as a speed multiplier. A car wheel is also a speed multiplied wheel and axle.
GEARS
Gears are just wheels and axles with teeth. Teeth off one gear fits perfectly into the teeth of another gear. When a gear is turned it makes another gear go faster. Whichever wheel moves first is the driving wheel. It's usually moved by a person or a motor. The wheel that is moved by a driving gear is a driven gear. In a hand operated egg beater, there are two driven gears. Imagine that!
Levers
Levers are the most simplest machines of all! It's always just a long bar that helps you apply a bigger force when you turn it. It uses the turning effect of a force. There are three types of levers, first-class, second-class and third-class levers. The turning point of a lever is called the fulcrum, the motion that a lever is usually working against is called a load. And a force used to cause movement would be called the effort.
For example, a see-saw is a lever, a first class lever. You are the load, the balance-point in the middle would be the fulcrum and the other person would be the force. First class levers have a fulcrum that lies between the effort and the load. First class levers are called force multipliers. A force multiplier is a simple machine that supply a bigger force than the effort used. The effort must be applied over a greater distance than the load is moved.
Second-class levers are also force multipliers, but the load is between the fulcrum and the effort. Wheelbarrows, butcrackers and sliding doors are all examples of second-class levers.
Force multipliers are good because they allow you to move a huge load without applying a lot of big effort.
Third class levers are levers with the effort between the fulcrum and the load. They are not force multipliers, they're speed multipliers. Speed multipliers are simple machines that increases the speed of an object. You must apply a greater effort than the load, but apply it over a short distance. Golf clubs and tennis rackets are both third-class levers. Because the load would be the ball that you hit, the fulcrum your arm and the effort would be the amount of force you apply to the ball you are whacking.
Mechanical Advantage
The mechanical advantage of force multipliers can be found by divinding the load by the effort.
mechanical advantage = load/effort
For example, if you had a seesaw and there was a person of about 50 kilos acting as the load and a peson of 40 kilos as the effort the mechanical advantage would be 1.25.
mechanical advantage= 50/40= 1.25
Ramps and Screws
Ramps
Screws
Ramps are very useful in doing many every day things. They are used to raise object higher, but without having to physically lift it straight upwards.
A ramp is an inclined plane. An inclined plane is a simple machine that uses sloping surfaces to reduce the effort required for a task.
When you use a ramp, you use less effort than just lifting the article straight up. Although, it only takes a small amount of effort to push the article up a ramp, you have to push it further, therefore, you use the same amount of energy to push and lift.
Ramps are all over the place in our every day life.
They are used all over the place, for wheelchairs, getting things out of trucks and even at Grandma's house!
Screws are also machines. They are once again, inclined planes, since they are curved ramps. Some people, who look at them very, very, nearly you can see that, in actual fact, a screw is a ramp that has been chopped up a bit, that is called a thread. But, when using a screw, you don't push it upwards, you push a screw downwards into something, like a desk or table.
<- That is a ramp on the back of a truck...If you didn't know....
PULLEYS
Pulleys are made up of a wheel and a rope.
A pulley is a simple machine consisting of a grooved wheel, over which, a rope can move freely. Pulleys are used to increase forces and to change their direction.*
One fragment of the rope is attached to the load. When you pull on one side of the pulley, the wheel turns and the load will move. Pulleys let you move loads up, down, or sideways. Pulleys are good for moving objects to hard to reach places.
It makes life a whole lot easier, letting you move heavy loads without a care in the world.
All you have to do is pull the rope and bada-boom bada-bing, it's moved! Flag poles, blinds and cranes are all examples of pulleys.
* = Glossary term for Pulley out of Science Quest 2
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