Simple Machines in your world!

Imagine…• eating soup without a spoon• hauling dirt without a wheelbarrow• opening a door without a doorknob

…That is what life would be like without simple machines.

Machines are not limited to the complicated devices such as cars, computers,

and airplanes!• A machine is any

device that makes work easier.

• They make work easier by placing forces where we want them, by moving things faster, and by making forces larger.

Friction Review

FrictionFriction is the force we feel when is the force we feel when things rub against each otherthings rub against each other

The more things are pushed The more things are pushed together, the more friction there istogether, the more friction there is

It is the force that It is the force that opposesopposes motion motion..

Friction ReviewFriction slows down the movement of Friction slows down the movement of

things and turns motion into thermal things and turns motion into thermal energy (heat).energy (heat).

When you When you rub your hands togetherrub your hands together you can feel the thermal energy you can feel the thermal energy produced.produced.

The mucus from The mucus from aa slugslug will will decreasedecrease friction as the slug slides along the friction as the slug slides along the ground.ground.

Simple MachinesSimple Machines

The purpose of a simple machine is to

A. increase the speed of workB. change direction the force is acting inC. increase Mechanical Advantage

- a machine’s ability to multiply input force

Presenting the 6 simple machines:1. LEVER

2. INCLINED PLANE3. WEDGE4. SCREW

5. WHEEL AND AXLE6. PULLEY

Inclined Plane:

• A simple machine with no moving parts.

• It increases the distance the object moves, but it decreases the amount

of force needed to move it.• It is simply a straight slanted

surface.• An example - a ramp, roadways, slide, roadways, slide,

stairsstairs

Wedge:• An inclined plane

that moves.• Most are made of

TWO inclined planes.• Examples:

– ax– knife– and zippers!

Screw:• An inclined plane wrapped around a

central bar to form a spiral.• A screw increases the distance which

decreases the force needed.• Examples:

– Screws– Jar lids

Lever:• An arm that “pivots” (or turns)

around a fixed point• The fixed point is called the

fulcrum.• A lever increases the distance

to decrease the force required.• Examples:

– seesaw– wheelbarrow– fishing pole

Wheel and Axle:• A simple machine made up of 2

circular objects of different sizes.• The wheel is the larger object and

turns about the small object, (the axle).

• Because the wheel is larger than the axle, it moves a greater distance.

• Examples:– roller skates– doorknobs

Pulley:• A rope, belt, or chain

wrapped around a grooved wheel

• Works in 2 ways:– changes the direction of the

force• or

– changes the amount of force

• Examples:– flagpole– sails on a sailboat

So What??????• Like you heard at the beginning, machines make

work easier. The measure of how much easier is called the mechanical advantage.

• It is important to note that the work that comes out of a machine is never greater than the work put into a machine. In fact, machines actually require more energy to do the same job, even though they make the job easier!

• Most of the machines we use today are compound machines - two or more simple machines working together!