Simple Machines

Introduction to

What are they?

Simple machines are machines

with few or no moving parts

that are used to make work easier

Types of Simple Machines

Wedge

Wheel and Axle

Lever

Inclined Plane

Screw

Pulley

Wedge

• Pushes materials apart, cuts things

• Examples: axe, doorstop, chisel,

nail, saw, jackhammer, bulldozer,

snow plow, horse plow, zipper,

scissors, airplane wing, knife, fork,

bow of a boat or ship

The Wedge

• A wedge is used to

split, tighten, or secure

a hold.

• A wedge is usually a

triangle shape with a

sharp point.

• If you apply force at one

end, the wedge will go

between something, in

this case an ax splits a

piece of wood.

Where can we find wedges?

• Wedges that split:

• Your teeth!

• Every time you bite

into something, you

are using a wedge.

• Wedges that cut:

• A saw!

• A knife!

• Wedges that tighten:

• A doorstop to keep

the door open.

• Wedges that hold

things together:

• A nail holds wood to a

wall or other wood.

Wheel and Axle

• Makes it easy to move things by rolling them,

and reducing friction

• Examples: car, bicycle, office chair,

wheel barrow, shopping cart,

hand truck, roller skates

The Wheel and Axle

• Two or more wheels

are connected by an

axle.

• The wheel turns with

or around the axle.

• This car wheel has a

big axle that it

rotates around when

the car moves.

Why do we need wheels?

• Wheels help us move heavy objects.

• They roll easily.

• Did you know a doorknob is really two

wheels connected by an axle? You can’t

see the axle because it’s inside the

wheels, but it’s there!

• If there wasn’t an axle, the doorknob

wouldn’t turn!

Another kind of wheel is called a

gear! • A gear is a wheel with teeth.

• The teeth fit in between each other and

turn.

• When one gear turns, its teeth push

against the teeth of the other gear and

they both turn.

• There are gears on your bike, on a can

opener and on an egg beater.

Lever

• Makes lifting weight easier by using a fulcrum

to redirect force over a longer distance

• Examples: see-saw, dump truck, broom, crane

arm, hammer claw, crow bar, fishing pole,

screwdriver, bottle opener

Levers

• There are three

parts to a lever:

• Load

• Force

• Fulcrum: support or

balance

A seesaw is a lever

• Let’s pretend you are

riding a seesaw with your

friend.

• The center support is the

fulcrum, which does not

move.

• The load is your friend

sitting on one end.

• You exert the force at the

other end trying to lift

your friend off the ground.

• When you push down on your

seat, (the force) you can lift

your friend (the load) while the

fulcrum acts as the pivot point,

making the seesaw go up and

down.

• It’s easy to lift your friend this

way instead of just picking her

or him up by yourself!

Inclined Plane

• Makes it easier to move objects upward,

but you have to go further horizontally

• Examples: highway or sidewalk ramp,

stairs, inclined conveyor belts, switchback

roads or trails

The Inclined Plane

• It is a slanted surface

or ramp.

• It makes moving

objects easier.

• Roads are also

inclined planes.

Instead of going

straight up, like this:

roads go up at small

angles, like the

picture.

Screw

• Turns rotation into lengthwise movement

• Takes many twists to go a short distance

• Holds things together

• Examples: screws, bolts, clamps, jar lids,

car jack, spinning stools, spiral staircases

The Screw

• The three parts to a

screw:

• Head

• Shaft

• Tip

• The head is the part that

you exert a force on.

• The shaft has ridges,

called threads that wind

around the screw. If it

doesn’t have the threads,

it is probably just a nail.

• The tip is sharp.

How to use a screw:

• Fasten two things together

• When you turn it, the threads cut a groove

in the material, making a hole. The groove

holds the screw tightly in place.

• To remove the screw you turn it the

opposite way, you can’t just pull it out.

Pulley

• Makes lifting things with a rope easier

by redirecting force and the addition

of additional pulleys

• Examples: flag pole, elevator, sails,

fishing nets, clothes lines, cranes,

window shades and blinds, rock

climbing gear

Pulleys

• Lifting a bucket full of water

is a lot of work!

• A pulley is a wheel with a

rope running over it. The

wheel has a groove, called a

sheave, and it keeps the

rope from slipping off the

wheel.

• Remember, since there is a

wheel in a pulley there also

has to be an axle!

• These two men are using a

pulley to help them lift their

heavy bucket.

Why Use Simple Machines?

For the mechanical advantage…

• Making something easier to do,

but it takes a little longer to do it

• For example, going up a longer flight

of stairs instead of going straight up a

ladder

Complex Machines

• Combining two or more simple machines

to work together

• Examples:

– Car jack combines wedge and screw

– Crane or tow truck combines lever and pulley

– Wheel barrow combines wheel and axle

with a lever

Summary

Wedge Pushes material apart, cuts

Wheel

and Axle

Makes it easy to move things

by rolling them, and reducing friction

Lever Helps lift heavy weights

using longer distances

Inclined

Plane

Makes it easier to move objects upward;

a longer path, but easier lifting

Screw Turns rotation into lengthwise movement

Pulley

Makes lifting heavy weights easier

by redirecting force

Compound Machines

• Compound machines consist of two or

more simple machines put together.

• Most devices are compound machines.

• They can do more difficult jobs because

their mechanical advantage is greater.

Name the Simple Machines

Present in Each Compound Machine

Compound Machines

COMPOUND MACHINES

• A compound

machine is a

combination of

two or more

simple

machines that

operate

together.

COMPOUND MACHINES

• Many familiar

compound machines,

such as a car, a

washing machine, or a

clock, are

combinations of

hundreds or thousands

of simple machines.

Compound Machine

Corkscrew

• Inclined Plane

• Wedge

• Screw

• Lever

• Wheel and Axle

Compound Machine

Jack

• Inclined Plane

• Wedge

• Screw

• Lever

A Wedge in a Compound Machine:

Stapler

• Staples are

wedges: they cut

through paper

because their

ends are pointed

in a wedge shape.

• Simple machines

in a stapler:

– Wedge

– Lever

A Wedge in a Compound Machine:

Scissors

• The cutting edge

of scissors is a

wedge.

• Simple machines

in a pair of scissors:

– Wedge

– Lever