Chapter 11 Section 4 Simple Machines
What is a Simple Machine? Is a machine that takes one force and changes its direction, distance, or strength. A simple machine has few or no moving parts. Simple machines make work easier. Introduction
Simple Machines Effort – force you apply to a machine Output- the force a machine supplies Load- the object moved Simple machines can increase the force we apply.
Simple Machines Work = force x distance Simple machines make work easier because it can increase force needed to move objects or they can decrease the amount of force needed to move the object. Examples of simple machines are levers, pulleys, wedges, wheel & axle, inclined planes, and screws.
What are Levers ? A lever is a bar that rests on a support called a fulcrum which lifts or moves loads. Fulcrum- the pivot point for a lever Levers multiply effort, distance, and speed.
Levers-First Class In a first class lever the fulcrum is in the middle and the load and effort is on either side. The effort and out move in opposite directions. Think of a see-saw
Levers-Second Class In a second class lever the fulcrum is at the end, with the load and effort on one side. Think of a wheelbarrow Effort ^
Levers-Third Class In a third class lever the fulcrum is again at the end, but the effort is in the middle Think of a pair of chop sticks
Wheels and Axles The wheel and axle are a simple machine. The axle is a rod that goes through the wheel which allows the wheel to turn to lift or move loads. Gears are a form of wheels and axles
Pulleys Pulleys are wheels and axles with a groove around the outside used to raise or lower a load. A pulley needs a rope, chain or belt around the groove to make it do work.
Inclined Planes An inclined plane is a slanting surface connecting a lower level to a higher level. Inclined planes make the work of moving things easier.
Wedges Two inclined planes joined back to back. Wedges are used to split things. Wedges are also used to lift objects.
Screws A screw is an inclined plane wrapped around a pole which holds things together or lifts materials. The inclined plane allows the screw to move itself when rotated.
Compound Machines Compound machines- two or more simple machines used to move a load. A compound machine can also use the same simple machine multiple times. Efficiency- ratio of input energy to output work.
Compound Machine Bulldozer – lever and wedge Wheelbarrow- levers, wheel and axle, Scissors- levers and wedges Hand drill- screw and wheel and axle Elevator- multiple pulleys