Simple Machines Outline
Notes
Pages 124-135
 There are 6 basic kinds of simple machines: the inclined plane,
the wedge, the screw, the lever, the wheel and axle, and the
pulley.
1. Inclined Plane
 Inclined plane: flat, sloped surface
 Example: ramp
A. How It Works
 Allows you to exert you input force over a longer distance
B. Mechanical Advantage
 You can determine the ideal mechanical advantage of an
inclined plane by dividing the length of the incline by its height.
 Ideal mechanical advantage = length of incline ÷ height of
incline
2. Wedge
 Wedge: device that is thick at one end and tapers to a thin edge
at the other end.
 Examples: zipper, knife
A. How It Works
 Input forces exerted on a wedge causes the output forces to
push the wedge into the object.
B. Mechanical Advantage
 The ideal mechanical advantage of a wedge is determined by
dividing the length of the wedge by its width.
 The longer and thinner a wedge is, the greater its mechanical
advantage.
3. Screws
 Screw: inclined plane wrapped around a cylinder
 Examples: threads in a jar lid, bolt
A. How It Works
 Threads of a screw act like an inclined place to increase the
distance over which you exert the input force
B. Mechanical Advantage
 The ideal mechanical advantage of a screw is the length around
the threads divided by the length of the screw.
4. Levers
 Lever: rigid bar that is free to pivot or rotate on a fixed point
 Fulcrum: fixed point that a lever pivots around
A. How It Works
 When you push down, you exert an input force on the handle
which pivots on the fulcrum.
B. Mechanical Advantage
 The ideal mechanical advantage of a lever is determined by
dividing the distance from the fulcrum to the input force by the
distance from the fulcrum to the output force.
 Ideal mechanical advantage = distance from fulcrum to input force
÷ distance from fulcrum to output force
C. Different Types of Levers
 1st class: always change the
direction of the input force
 2nd class: increase force but do
not change the direction of the
input force
 3rd class: increase distance but do
not increase the direction of the
input force
5. Wheel and Axle
 Wheel and axle: simple machine made of 2 circular objects
fastened together that rotate about a common axis
 Examples: screw driver, doorknob
A. How It Works
 Increases to your force but you must exert your force over a
long distance.
B. Mechanical Advantage
 You can find the ideal mechanical advantage of a wheel and
axle by dividing the radius of the wheel by the radius of the
axle.
 Mechanical advantage = radius of wheel ÷ radius of axis
6. Pulley
 Pulley: simple machine made of a grooved wheel with a rope or
cable wrapped around it
A. How It Works
 You use a pulley by pulling on one end of the rope.
 Pulleys can decrease the amount of input force needed to lift
an object or it can change the direction of your input force.
B. Types of Pulleys
 There are 3 types of pulleys: a fixed pulley (attached to a
structure), a moveable pulley (attached to the object you are
moving), and a block and tackle (combination of a fixed an a
moveable pulley).
 The ideal mechanical advantage of a pulley is equal to the
number of sections of rope that support the object.
7. Simple Machines in the Body
A. Living Levers
 Most of the machines in your body are levers that consist of
bones and muscles.
B. Working Wedges
 Your teeth are wedges
8. Compound Machines
 Compound machine: machine that utilizes 2 or more simple
machines
 The ideal mechanical advantage of a compound machine is the
product of the individual ideal mechanical advantages of the
simple machines that make it up.