Unit 4 Topic 1 Levers Inclined Planes Topic

Unit #4 Topic #1 Levers & Inclined Planes

Topic #1 – Levers & Inclined Planes n n n A lever is a simple machine that changes the amount of force you must exert in order to move an object It consists of a bar that is free to rotate around a fixed point called the fulcrum Examples of levers are: screwdrivers, bottle openers, hockey sticks, scissors, wheelbarrows, teeter-totter, etc.

n n n The force you exert on a lever to make it move is called the effort force. The load is the mass of an object that is moved or lifted by a machine such as a lever. In other words, the load is the resistance to movement that a machine must overcome.

n n The distance between the fulcrum and the effort force is called the effort arm. The distance between the fulcrum and the load is called the load arm.

Class 1 Levers n n There are 3 classes of levers, depending on the location of the fulcrum, effort force and load. Class 1 levers have the fulcrum between the effort and the load (teeter-totter or seesaw) Class 1 levers are used for power or precision

Class 2 Levers n n Class 2 levers have the load between the effort and the fulcrum (wheelbarrow) Class 2 levers exert a greater force on the load than the effort force you exert on the lever (wheel barrows or bottle opener)

Class 3 Levers n n Class 3 levers have the effort between the fulcrum and the load (hockey stick) Class 3 levers require a greater force be exerted on the lever than the lever exerts on the load (hockey stick or fishing rod)

What is Work? n n n Some of you may think work is school or homework or chores at home. However, work can actually be calculated with the formula Work = Force x distance (W=Fd) Work, like energy is measured in units called joules (J)

Inclined Planes n n n An inclined plane is a ramp or slope that reduces the force you need to exert to lift something. Inclined planes are also simple machines! Examples of inclined planes are: wheelchair ramps, loading ramps in factories, etc.

Work Input and Work Output n n When you do work on a machine such as a lever, the machine does work on the load. The work you do on a machine is called the input work. The work the machine does on the load is called the output work. Important!!! – a machine never does more work on the load than you do on the machine.

n n n Machines make work easier because they change the size or the direction of the force exerted on the load Mechanical advantage is the comparison of the force produced by a machine to a force applied to a machine. In other words, mechanical advantage is the comparison of the size of the load to the size of the effort force.

Mechanical advantage can be calculated by the following formula: MA = FL/FE (where FL is load force and FE is effort force) n Suppose Liam loved school so much he wouldn’t leave at the end of the day. I need to go home so I plan on lifting Liam onto a cart to wheel him out the door. However, my enormous muscles cannot handle such a load so I decide to use a lever to lift him out of his chair. If Liam is exerting a force of 100 N on the chair and I only have to exert a force of 20 N to move him, what is the mechanical advantage? n

MA = Load force/effort force = 100 N/20 N =5 Therefore, the lever I used has exerted a force 5 times greater than the force I exerted on it!!!! n Luckily for me, Liam didn’t fight back or he would have crushed me with his enormous “pipes”.

Another way to calculate MA is by the following formula: MA = Effort arm/ Load arm Lets say the lever I used to lift the massiveness of Liam was 6 m long. If the effort arm was 5 m and the load arm was 1 m the MA = 5 m/1 m =5 n

Inclined Planes n n n These might be the simplest of the simple machines An inclined plane is simply a ramp that makes moving something from a lower place to a higher place (or vice versa) simpler Examples are ramps for wheelchairs, shopping carts, loading ramps, etc