Simple Machines Devices that “make work easier”

Or do they???• Work DOES NOT become easier – the

object still has to move through the same distance

• The amount of input, or effort force, needed to move that object is what becomes easier or less

• People use simple machines to lessen the input/effort force they need to apply (which is what we call “work”)

There are technically 6 types…

• Inclined Planes • Wedges• Screws• Pulleys• Wheels and

Axels• Levers

Inclined Planes• A flat, slanted surface that

makes it easier to move heavy objects to higher or lower levels

Connection to station: • Gives mechanical advantage to

person by moving large object with less effort; must move it for a longer distance though

Wedges• An inclined plane that is used as

a tool for cutting or separating things, or keeping things from moving Connection to

station:• Thicker wedges leave larger cuts but also have more resistance which needs a larger force to create the same cut• Bolt does not have point (wedge)

Screws• An inclined plane wrapped in a

spiral around a cylinder or cone

Connection to station:• A right triangle is an

inclined plane• A screw is a right

triangle around a rod

Pulleys• A wheel with a groove in the rim

which a rope fits into• Two types of pulleys:–Fixed – changes the direction

of the effort force, but the force must equal the load–Moveable – decreases the

effort force needed to move the load, but the rope moves a long distance to move the load a short distance

Pulleys Continued Connection to station:• Set-up 1 – kind of difficult to lift

jug (fixed)• Set-up 2 – easier than first one but

more rope needed (movable)• Set-up 3 – easiest of

all, but lots more rope needed (combination of fixed and movable)• More pulleys = more

rope needed

Wheels and Axles• Wheels rotate in a circle

around an axle; axle causes wheels to move

Connection to station:• No S.M. – very difficult to move books• Wheels only – person does most work

by having to manually move wheels• Wheels and axles – the axles turn the

wheels which decreases the needed effort force

Gears (the 7th S.M.)• Wheels and axles with teeth

Click here to understand how gears work

Levers• A straight bar that rests on

a fulcrum • Helps you lift heavy loads or

change direction of force

Click here to help better understand the 3 different classes of levers

Levers ContinuedConnection to station:• This was example of 1st class

lever (pencil was always between F and L)• Closer the fulcrum is to the

load, the less force needed to lift