Simple and Mechanical Advantage Simple Machines

Ancient people invented simple machines that would help them overcome resistive and allow them to do the desired work against those forces. Simple Machines

• The six simple machines are: – – Wheel and Axle – – Inclined Plane – Wedge –

Simple Machines

• A is a device that helps make work easier to perform by accomplishing one or more of the following functions: – transferring a from one place to another, – changing the direction of a force, – increasing the magnitude of a force, or – increasing the distance or speed of a force.

Mechanical Advantage

• It is useful to think about a machine in terms of the input force (the force you apply) and the output force (force which is applied to the task). • When a machine takes a small input force and increases the magnitude of the output force, a mechanical advantage has been produced. Mechanical Advantage

• Mechanical advantage is the ratio of output force divided by input force. If the output force is bigger than the input force, a machine has a mechanical advantage greater than one. • If a machine increases an input force of 10 pounds to an output force of 100 pounds, the machine has a mechanical advantage (MA) of 10. • In machines that increase distance instead of force, the MA is the ratio of the output distance and input distance. MA = output/input No machine can increase both the magnitude and the distance of a force at the same time. The 6 Simple Machines

Inclined Plane Screw Wedge

Pulley Wheel and Axle Lever Inclined Plane Inclined Plane • The Egyptians used simple machines to build the pyramids. One method was to build a very long incline out of dirt that rose upward to the top of the pyramid very gently. The blocks of stone were placed on large logs (another type of - the wheel and axle) and pushed slowly up the long, gentle inclined plane to the top of the pyramid. Inclined Planes • An inclined plane is a flat surface that is higher on one end • Inclined planes make the work of moving things easier The Lever

• A lever is a rigid bar that rotates around a fixed point called the fulcrum. • The bar may be either straight or curved. • In use, a lever has both an effort (or applied) force and a load (resistant force). There are 3 Classes of

• Depends on the location of 3 items: 1. Fulcrum – fixed point  EA  on a lever 2. Effort Arm – the part of the lever that exerts the effort force. 3. Resistance Arm – the RA part of the lever that exerts the resistance force. 1st Class Lever

– Changes the direction of the force – Multiplies effort force – Magnifies speed and distance – Ex: seesaw, crowbar, scissors 2nd Class Lever

– Multiply effort force – Mechanical advantage is always greater than 1. – Ex: bottle opener, boat oars, wheel barrow 3rd Class Lever

– Magnifies speed and distance – Mechanical Advantage always less than 1 – Ex: baseball bat, golf club, broom, shovel WHEEL AND AXEL • The axle is stuck rigidly to a large wheel. Fan blades are attached to the wheel. When the axel turns, the fan blades spin. Pulleys • Pulley are wheels and axles with a groove around the outside • A pulley needs a rope, chain or around the groove to make it do work Diagrams of Pulleys Fixed pulley: A fixed pulley changes the direction of a force; however, it does not create a mechanical advantage.

Movable Pulley: The mechanical advantage of a moveable pulley is equal to the number of ropes that support the moveable pulley. COMBINED PULLEY • The effort needed to lift the load is less than half the weight of the load. • The main disadvantage is it travels a very long distance. Mechanical Advantage

• Ratio of Output Force to Input Force • Follows simple pattern with Ropes and Pulley system Rube Goldberg Machines

• Rube Goldberg machines are examples of complex machines. • All complex machines are made up of combinations of simple machines. • Rube Goldberg machines are usually a complicated combination of simple machines. • By studying the components of Rube Goldberg machines, we learn more about simple machines