Simple Machines Making Life Easier Through Physics

Work and Energy Energy is conserved – you can’t create it or destroy it Work is transferring energy from one object to another Simple machines can’t increase or decrease the amount of work you do

Calculating Work Work doesn’t change when you use a machine Most simple machines make our lives easier by DECREASING the amount of force we need to apply to finish a job –If you decrease the force, the distance must increase Some DSECREASE the distance instead –If you decrease the distance, the force must increase

Types of Simple Machines Lever Family –Lever –Pulley –Wheel and axle Inclined Plane Family –Inclined plane –Wedge –screw

Lever Rigid arm with a turning point Turning point is called the fulcrum Moves force to a new location –Resistance force is the force the lever applies to an object –Effort force is the force a person applies to the lever Three classes of levers

1 st class levers Effort force and resistance force are on opposite sides of the fulcrum Seesaws are a first class lever fulcrum Effort forceResistance force

2 nd class levers Resistance force is between the fulcrum and the effort force wheelbarrows are a second class lever fulcrum Effort forceResistance force

3 rd class levers Effort force is between the resistance force and the fulcrum Your biceps are a third class lever fulcrum Effort force Resistance force

Wrap-Up #1 Classify the following levers by class 1.Scissors 2.Fishing rod 3.Stapler

Wrap-Up #1: Answers Classify the following levers by class 1.Scissors 1 st class – handle has effort force, the joint is the fulcrum and the blades apply the resistance force 2.Fishing rod 3 rd class – fulcrum by your body, handle has effort force and the line has the resistance force 3.Stapler 2 nd class – the pivot is the fulcrum, you push in the middle and the staple is the resistance force

Pulleys The middle point is like the fulcrum of a lever Mechanical advantage is equal to number of ropes Three kinds –Fixed pulley –Movable pulley –Block and tackle (multiple pulleys at the same time)

Wheel and Axle Pulley (wheel) connected to a shaft (axle) Small force on the large wheel is turned into a bigger force on the smaller axle Screwdrivers are also wheel and axles

Inclined Plane Allow you to apply a horizontal force to move things up You use less force than if you lift straight up You apply the force over a longer distance, so the work doesn’t change

Wedge Changes the direction of the force and splits it into two –If you push down the wedge pushes to the left and right Useful for splitting things like firewood and your food Nails are wedges used to hold things together instead

Screw An inclined plane wrapped around a cylinder Allows you to twist it into place instead of pushing straight down Allows a longer plane than if it was straight (spiral staircase)

Wrap-Up #2 Classify each of these images as a type of simple machine #1

Wrap-Up #2 Classify each of these images as a type of simple machine SCR EW Classify each of these images as a type of simple machine #1

Wrap-Up #2 Classify each of these images as a type of simple machine #2

Wrap-Up #2 Classify each of these images as a type of simple machine INCLIN ED PLANE Classify each of these images as a type of simple machine #2

Wrap-Up #2 Classify each of these images as a type of simple machine #3

Wrap-Up #2 Classify each of these images as a type of simple machine PUL LEY Classify each of these images as a type of simple machine #3

Wrap-Up #2 Classify each of these images as a type of simple machine #4

Wrap-Up #2 Classify each of these images as a type of simple machine LEV ER Classify each of these images as a type of simple machine #4

Mechanical Advantage A measure of how much the machine helps you –MA < 1, you apply a stronger force over a smaller distance –MA = 1, the force’s direction is changed –MA > 1, you apply a lower force over a greater distance

Efficiency Some energy (work) is always converted into heat by friction The percentage of work transferred by the machine is its efficiency Higher efficiency means less friction