PHYSICAL SCIENCE - CHAPTER 9 LESSON 3 - INCLINED PLANES & LEVERS WITH VERIFIED FOR ACCURACY

How do inclined planes work? An inclined plane allows you to exert your input force over a longer distance. As a result, the input force needed is less than the output force. Simple Machine Is the most basic device for making work easier. What are 3 closely related simple machines from the inclined plane family? Inclined plane Wedge Screw What is a ramp an example of? A ramp is an example of a simple machine called an inclined plane. Inclined Plane Is a flat, sloped surface. What is the input force you use on an inclined plane? It is the force with which you push or pull an object along the slope. What is the inclined plane's output force equal to? It is equal to the object's weight. How can you determine the ideal mechanical advantage of an inclined plane? By dividing the length of the incline by its height. Wedge Is a device that is thick at 1 end & tapers to a thin edge at the other end. EX: knife & zipper How do wedges work? When you use a wedge, instead of moving an object along the inclined place, you move the inclined plane itself. EX: When an ax is used to split wood, the ax handle exerts a force on the blade of the ax, which is the wedge. That force pushes the wedge down into the wood. The wedge in turn exerts an output force at a 90 degrees angle to its slope, splitting the wood in 2. How do you determine the ideal mechanical advantage of a wedge? By dividing the length of the wedge by its width. The longer & thinner a wedge is, is the mechanical advantage greater or smaller? Greater 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. How do screws work? The threads of a screw act like an inclined plane to increase the distance over which you exert the input force. What happens as the threads of the screw turn? As the threads of the screw turn, they exert an output force on the wood. Friction holds the screw in place. What are other examples of screws? Bolts Drills Jar lids How do you determine the ideal mechanical advantage of a screw? Length around the thread divided by the length of the screw. What happens if the threads of a screw are closer together? The mechanical advantage is greater. How are levers classified? Levers are classified according to the location of the fulcrum relative to the input & output forces. Lever Is a rigid bar that is free to pivot, or rotate on a fixed point. Fulcrum The fixed point that a lever pivots around. How Do Levers Work To understand how levers work, think about using a spoon. Your wrist acts as the fulcrum. The bowl of the spoon is placed near your food. When you turn your wrist, you exert an input force on the handle, & the spoon pivots on the fulcrum. As a result, the bowl of the spoon digs in, exerting an output force on your food. Mechanical Advantage of a Lever Using a lever like a spoon doesn't increase your input force or change the direction of your input force. Instead, it increases your input distance. When you use a spoon, you only have to move the handle a short distance in order to scoop up food over a longer distance. However, you need to apply a greater force than you would have without the spoon. How do you determine the mechanical advantage of a lever? By dividing the distance from the fulcrum to input force by the distance from the fulcrum to output force. First - Class Levers First - class levers change the direction of the input force. They also increase force or distance. Force increases if the fulcrum is closer to the output force. Distance increases if the fulcrum is closer to the input force. The fulcrum is always in the middle. .Example of First - Class Levers Seesaws Scissors Neck Second - Class Levers Second - class levers increase force. They don't change the direction of the input force. Output force is always in the middle. Example of Second - Class Levers Doors Nutcrackers Bottle openers What is the mechanical advantage of second - class levers? It is always greater than 1. Third - Class Levers Third - class levers increase distance, but don't change the direction of the input force. The input force is always in the middle. Examples of Third - Class Levers Spoons Shovels Baseball bats What is the mechanical advantage of third - class levers? It is always less than 1.