When people think about machines, they probably think about airplanes, cars, power saws, or any other machine that has a motor. What they may not think about is the fact that not every machine needs a motor for it to run. Tennis racquets, bottle openers, nails, and scissors are all considered machines and the only thing needed to make these machines work is you! Even though these objects have no motor, they are still machines because they perform a job. These types of machines are known as simple machines. Using simple machines can help in increasing force, changing direction, increasing elevation of heavier things, pull, split, fasten, cut, lift, and go faster. You are working when you are using force to cause a motion. Continue reading to learn about simple machines such as wheels and axles, inclined planes, levers, pulleys, screws, and compound machines.
Wheels and Axels
A wheel is used to increase force and distance. A gear is a special kind of axle and wheel. Examples include airplane propellers, door knobs, bike pedals, water faucets, and car wheels. When you turn a door knob there is a large knob turning a smaller knob. Distance is being traded for force. For instance, when a bicycle axle is being turned with the pedals you are getting a greater amount of distance as the bigger wheel turns.
An inclined plane stays still. It allows for less force over greater distances. Escalators, ladders, stairs, and ramps are examples of inclined planes. They are sloping surfaces used in lifting heavier loads without a lot of effort. Rollers and inclined planes played a role in the pyramids being built in Egypt and replaced limestone blocks which weighed about seventy tons each.
A lever allows for less force to be used over greater distances or more force to be used over shorter distances. It trades one for the other. Bottle openers, crowbars, seesaws, and claw hammers are examples of levers. Levers have three parts. The resistance force is the object being lifted or moved; the effort force is the work done using the lever; and the fulcrum is a fixed point that pivots. Levers vary depending on where the fulcrum is. For instance, on a seesaw the fulcrum is between what you want to move and the force. With a bottle opener the fulcrum is on one end while the force is at the other. What is being moved is in the middle. With a tennis racquet, the fulcrum is on one end, the object being moved at the other, and the force is in the middle.
A pulley is a wheel that holds a rope with a grooved rim. When the pulley is fixed, it only changes the forces direction but not the force, speed, or distance. When you are opening a mini-blind, curtain, or lifting a flag onto a pole, a pulley is being used. With a pulley a rope can be pulled and the load can be lifted using body weight. Pulleys are also wheels turning around axles.
Screws are inclined planes wrapped around cylinders. Screw threads form tiny ramps which go around the actual screw. These allow for the use of less force and the changing in the forces direction. Lids, jars, boat propellers, piano stools, meat grinders, and helicopter blades are all examples of screws. Bolts and nuts are also types of screws which help in fastening things together. Most machines have some type of screw in them.
Compound machines are simple machines added together. Most machines are considered to be compound machines. These machines can handle difficult jobs that a simple machine alone may not be able to. They also have a greater mechanical advantage. Examples of compound machines include bicycles and scissors.
Visit the links below to learn more about simple and compound machines:
- Understanding Simple Machines - Use these online activities to learn more about motion and how simple machines work. You can play interactive games such as Clunky Cogs, Pick the Bits, and Balancing Frogs.
- Simple Machines Discovery Box - This booklet provides activities to help kids learn more about inclined planes, pulleys, construction, gears, pendulums, and more.
- Simple and Complex Machines - Here you can learn about wedges and levers, pulleys and inclined planes, and wheels and axles through interactive activities.
- Ed Heads - This game allows kids in grades two through six to learn about simple machines by exploring a tool shed and house.
- Inventor's Toolbox - Use the inventor's toolbox to learn more about simple machines as well as other elements of machines.
- Marvelous Machines - This is a list of simple machine experiments for third grade students. You can conduct experiments using springs, friction, pulleys, gears, levels, wheels, and inclined planes.
- PBS - Sid the Science kid teaches you more about simple machines through online and classroom activities.
- Simple Machines Experiments - This website provides instructions on simple machine experiments which include levers, pulleys, wheels, and ramps.
- Bill Nye the Science Guy - Watch this video about simple machines from Bill Nye the Science Guy.
- Simple Machine Games - Here you can play a concentration and a matching game about simple machines.
- Museum of Science and Industry - Here you can play the Ultimate "Twitch" game about simple machines.
- MiKids - This website provides activities about simple machines and quizzes for you to test your newfound knowledge.
- Medieval Levers - Here you are introduced to medieval levers and then asked to build your own. You can then have fun testing it out.
By: Daniel Watson