14-4 Simple Machines Objectives 1. What are the 6 types of simple machines? 2. What determines the MA of the 6 types of simple machines?

*Simple Machines are divided into 2 families: 1. The Lever Family 2. The Inclined Plane Family

The Lever

The Lever a rigid bar that is free to turn about a fixed point called the fulcrum Every Lever has three (3) parts: 1.  Resistance Force, Input Force or Load, What you are trying to move or lift. 2.  Effort Force or Output Force - The work done on the Lever. 3.  Fulcrum – A fixed pivot point.

The Lever

1st Class Lever

1st Class Lever The Fulcrum (fixed pivot point) is located between the Effort (Input) and the Resistance (Output) Forces.  The effort and the resistance move in opposite directions.  The effort force pushes down in order to lift the resistance or load.

1st Class Lever When the fulcrum is closer to the effort than to the load: there is a loss in force There is a gain in speed and distance.

1st Class Lever When the fulcrum is closer to the load than to the effort: there is a loss in speed and distance There is a gain in force.

1st Class Lever When the fulcrum is midway between the effort and the load: there is no change in force, speed or distance

1st Class Lever Examples: Seesaw Crowbar Scissors

2nd Class Levers

2nd Class Lever The load is between the effort and the fulcrum. The fulcrum is at one end of the lever. The fulcrum is usually closer to the load. Produce a gain in force.

2nd Class Levers Examples: Wheelbarrow Bottle opener Nutcrackers

3rd Class Levers

3rd Class Levers The effort is between the load and the fulcrum. There is usually a loss in force, but a gain in speed and distance.

3rd Class Levers Examples: Broom Shovel Fishing rod

The Pulley

The Pulley A pulley changes the direction of the force: Instead of lifting up, you can pull down using your body weigh against the load (what is being lifted) A pulley gains nothing in force, distance or speed

The Pulley a wheel that turns around an axle A pulley is a grooved wheel that turns around an axle (fulcrum), and a rope or a chain is used in the grove to lift heavy objects. A pulley may be fixed, moveable, or used in combination.

The Fixed Pulley Is attached to something that doesn't move such as the ceiling or wall) It acts as a first class lever with the fulcrum located at the axis Instead of a bar the pulley uses a rope or chain.

The Moveable Pulley A moveable pulley acts as second class lever the load is between the fulcrum and the effort

The Compound Pulley A compound pulley is a system of movable pulleys. Mechanical advantage can be increased by using more than one pulley.

The Wheel & Axle

The Wheel & Axle a wheel connected to a rigid pole The Wheel & axle is a modified lever: The center of the axle acts as a fulcrum – making the wheel a lever that rotates around in a circle.

The Inclined Plane Family consists of : the inclined plane, the wedge, and the screw

The Inclined Plane The Inclined Plane is a sloping surface, such as a ramp. It is one of the most important machines in industry. The inclined plane makes lifting or moving an object easier.

The Inclined Plane If you push an object up a ramp, you must move it a longer distance than if you tried to lift it straight up, but less effort is needed to move it. By using the inclined plane, the same amount of work is done, but the work is done in an easier way.

The Inclined Plane a sloping surface that does not move An inclined plane provides for NOT Less work but less effort.  The trade off is greater distance to travel.

The Inclined Plane Used to reduce the force needed to overcome the force of gravity when lifting or lowering a heavy object. MA = distance of plane / height

The Inclined Plane

The Wedge

The Wedge an inclined plane that tapers to a sharp edge The wedge used to increase force.  The material remains in place while the wedge moves through it. A wedge changes the direction of the input force.

The Wedge - A wedge is a small inclined plane used as a tool. - It acts as a moving inclined plane. - A wedge is usually a piece of wood or metal that tapers to a thin edge.

The Wedge It is used to raised an object or to split an object apart. -For example, when a door wedge is jammed under a door, it raises the door slightly and exerts a strong force against it. An axe is a wedge attached to a shaft.

The Wedge It changes a forward movement into a parting movement that can split a log. Nearly all cutting machines make use of the wedge, including scissors, saws, and knives. A nail is a wedge too.

The Wedge Wedges can be forced between two things to hold them tightly together, like nails or a doorstop. Wedges can be used to split, cut or fasten.

The Screw

The Screw A screw is an inclined plane wrapped around a cylinder. Like pushing an object up a ramp, tightening a screw with gently sloping threads requires a small force acting over a large distance.

The Screw Tightening a screw with steeper threads requires more force. Jar lids are screws that people use everyday. Spiral staircases are also common screws.

The Screw an inclined plane wrapped around a central cylinder A Screw has two (2) parts: The Body – Cylinder Post The Thread – Inclined Plane wrapped around the cylinder.

The Screw Functions of the screw To fasten things – the standard screw or nuts & bolts. Drill bits are screws used to make holes. A jackscrew is used to lift heavy objects; car jack.

The Screw When you turn a screw: The input force is changed by the threads into an output force. The output force pulls the screw into the materials. Friction between the threads & the material holds the screw in place.

The Screw

Go back to page 70 and answer the 14-4 Objectives again. 1. What are the 6 types of simple machines? 2. What determines the MA of the 6 types of simple machines?