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Simple Machines
Mrs. Constantine Simple Machines Review
| Question | Answer |
|---|---|
| What is work | You do work on an object when you exert a force on the object that causes the object to move some distance. |
| Can there be work without motion? | In order for you to do work on an object, the object must move some distance as a result of your force. |
| In order to do work on an object, what must be in the same direction as the object's motion? | The force you exert must be in the same direction as the object's motion. |
| How can you calculate work (what is the formula)? | work= force x distance The amount of work done on an object can be determined by multiplying force times distance. |
| What is a Joule? | One joule (J) is the amount of work you do when you exert a force of one newton to move an object a distance of 1 meter. |
| What is a machine? | A machine is a device with which you can do work in a way that is easier or more effective. |
| How does a machine make work easier? | A machine makes work easier by changing the amount of force you exert, the distance over which you exert your force, or the direction in which you exert your force. |
| What is input force? | The force you exert on the machine. Also known as effort force. |
| What is output force? | This is the force exerted by the machine. Also known as resistance force. |
| Name the six different types of simple machines. | Inclined plane, wedge, screw, lever, wheel and axle, and pulley. |
| What is an inclined plane? | This is a flat, slanted surface. IT allows you to exert your input force over a longer distance. The input force necessary will be less than the output force. |
| How do you determine the advantage of an inclined plane? | Ideal mechanical advantage= length of incline/height of incline. (You can determine the ideal mechanical advantage of an inclined plane by dividing the length of the incline by its height). |
| Name one way to increase the efficiency of an inclined plane? | You can decrease the friction (ex: add wheels, like a dolly). |
| What is a wedge? | A wedge is a device that is thick at one end and tapers to a thin edge at the other end. It might be helpful to think about a wedge as an inclined plane (or two inclined planes, back to back) that can move. |
| Name two devices that depend on the wedge? | A zipper and an axe. |
| What is a screw? | Like a wedge, a screw is a simple machine that is related to the inclined plane. A screw can be thought of as an inclined plane wrapped around a cylinder. This spiral inclined plane forms the threads of the screw. |
| What is a lever? | It is a rigid bar that is free to pivot, or rotate, about a fixed point. |
| What is a fulcrum? | This is the fixed point around which a lever pivots. |
| What types of levers are there? | There are three classes of levers: first class, second class, and third class. |
| What is a first class lever? | These levers multiply force when the fulcrum is close to the output force. Otherwise they multiply distance. Examples of this are scissors, pliers, seesaws. |
| What is a second class lever? | These levers multiply distance but do not change the direction of the input force. Examples include fishing poles, shovels, baseball bats. |
| What is a third class lever? | These levers always multiply force. They do not change direction of the input force. They include doors, nutcrackers, and bottle openers. |
| How can you calculate the ideal mechanical advantage of a lever ? | You can calculate the ideal mechanical advantage of a lever by using the distances between the forces and the fulcrum: ideal mechanical advantange=Distance from fulcrum to input force/Distance from fulcrum to output force. |
| What is a wheel and axle? | This is a simple machine made of two circular or cylindrical objects that are fastened together and rotate about a common axis. The larger object is called the wheel and the smaller object is called the axle. |
| Give an example of a wheel and axle. | A screwdriver: In a screwdriver, the handle is the wheel, and the shaft is the axle. Every time you turn a doorknob, you use a wheel and axle. |
| How does a wheel and axle make work easier? | You apply an input force to turn the wheel, which is larger than the axle. As a result, the axle rotates and exerts an output force to turn something---it multiplies your force, but you must apply force over a longer distance. |
| How do you calculate the ideal mechanical advantage of a wheel and axle? | You use the radius of the wheel and the radius of the axle. Ideal mechanical advantage= radius of wheel/radius of axle. |
| What is a pulley? | It is a grooved wheel with a rope (or chain, or steel cable) wrapped around it. You pull on a rope, which changes the amount and direction of your input force. |
| What are the two types of pulleys? | Fixed and movable. |
| What is a fixed pulley? | This is a pulley that you attach to a structure. A single pulley can be used to raise a sail. |
| What is a movable pulley? | If you attach a pulley to an object you would like to move, then it is a movable pulley. |
| What is the ideal mechanical advantage of a pulley? | The ideal mechanical advantage of a pulley system is equal to the number of sections of the rope that support the object. |
| What is a compound machine? | This is a machine that uses two more more simple machines. A mechanical pencil sharpener is a good example. You turn the handle (wheel and axle) and the two cutting screws sharpen the pencil. |
| How do you calculate the advantage of a compound machine? | You need to know the mechanical advantage of each simple machine. The overall mechanical advantage is the product of the individual ideal mechanical advantages of the simple machines. |
| What are gears? | Inside the pencil sharpener, there is an axle that turns gears. A system of gears is a toothed wheel that fit into one another. Turning one wheel causes another to turn. |
Created by:
Heatherjane7101