1
Simple Machines
Students will investigate the relationship between force, mass, and the motion of objects.
Demonstrate the effect of simple machines (lever, inclined plane, pulley, wedge, screw, and wheel and
axle) on work.
Work
In science, the word work has a different meaning than you may be familiar with in your everyday life.
The scientific definition of work is:
The transfer of energy when a ____________________ moves an object over a ________________
in the same __________________ of the force.
If no ____________________ happens, no ________________________ is done.
Work = force x distance (W = Fd)
Work (joules) = applied force (newtons) X distance (meters)
1 J = 1 N · m
Examples: pushing a shopping cart, turning a door knob, kicking a soccer ball, lifting a box
Work or Not Work? (Write Yes or No)
According to the scientific definition, what is work and what is not?
a teacher lecturing to her class
a mouse pushing a piece of cheese with its nose across the floor
A scientist delivers a speech to an audience of his peers.
A bodybuilder lifts a dumbbell above his head.
A student pushes against a wall that does not move.
A father pushes a baby in a carriage.
A woman carries a grocery bag to her car.
Simple Machines
A device that makes work ____________ by changing the
____________________________________________________________ used to do the work.
A simple machine does not help you to do _________________ work.
Work with a simple machine = Work without a simple machine
No machine can increase _____________ the magnitude of the force and the distance an object travels at
the same time.
Therefore, there is a trade-off between ________________ and ____________________.
Work
Work Input (Win)
work done _______ a machine
Win = Fin x din
Work Output (Wout)
 work done _______ a machine
 Wout = Fout x dout
Energy: the ability to do _____________________
Law of Conservation of Energy
Energy can never be _____________________ or ___________________________.
Energy can be ________________ from one form to another.
You can _______________ get more work out than what you put in.
2
In an ideal machine: Win = Wout
In an real machine: Win > Wout
some energy (output force) is given off (“lost”) as ________________________
Force
Remember: A force is a push or a pull.
Effort Force (Fe)
Force that is applied ________ the machine
“What ________ do”
Also called the _________________ force
Resistance
Force (Fr)
that is applied ____________ the machine
“What the _______________ does”
Also called the ______________ force
Force
Mechanical Advantage
number of times a machine _________________ the effort force
 MA > 1 : ______________ is increased
 MA < 1 : __________________ is increased
 MA = 1 : only __________________ is changed
6 Kinds of Simple Machines
Inclined Plane Family
Inclined Plane
Wedge
Screw
Lever Family
Lever
Wheel and Axle
Pulley
Inclined Plane
A straight, slanted surface used to _____________ objects because it
is higher on one end
Examples: Ramps, stairs, ladders
Inclined planes make work easier by increasing the _____________,
decreasing the amount of force needed to move an object.
Wedge
A _______________ inclined plane with 1 or 2 sloping sides
Examples: knives, hatchets, ax blade, blades of scissors, nails, teeth
A wedge transfers force in one direction into force in two directions.
Wedges are used to ______________________ things apart.
The _________________ and _____________________ the wedge, the
easier the work.
Wedges still have to deal with ______________________.
3
Screw
A screw is an _________________________ wrapped around
a shaft or cylinder.
Examples: a fastener (screw), jar lid, drill bit, light bulb, vise
The inclined plane allows the screw to _________________
itself when rotated.
The _______________ the threads, the ______________ the
length of the inclined plane = work easier
Turning a screw  you apply a small force over a long
distance
Lever
a bar that pivots at a fixed point called a ________________
The 3 Classes of Levers
The class of a lever is determined by the location of the effort force, the load, and the fulcrum.
Effort force (input force): the force applied to the lever
Load (output/resistance force): the object being moved
First Class Lever
fulcrum is located ____________________ the effort force and
resistance force (load)
can increase ____________________________________
always changes the ______________ of force (i.e. a downward
effort force on the lever results in an upward movement of the
resistance force)
Examples: crowbars, scissors, pliers, tin snips, shovels, and seesaws
Second Class Lever
the load (resistance) is located _______________ the
fulcrum and the effort force
always increases ________________________
does not change the ___________________ of force
effort force moves farther than resistance
When the load is located _________________ to the
fulcrum than to the effort force, an _______________
(mechanical advantage) results
Examples: nut crackers, wheel barrows, doors, and bottle openers
Third Class Lever
the ___________________ is applied between the
fulcrum and the resistance force (load).
always increases the ______________ that the effort
force travels
does not change the ________________ of force
always produce a gain in speed and distance and a
corresponding decrease in force.
Examples: arm, tweezers, hammers, baseball bats, brooms, and rakes
4
Wheel and Axle
two wheels of different sizes that _______________ together
the wheel is always larger than the axle
a pair of __________________________
Examples: door knob, gears, car axle, pencil sharpener,
screw driver, faucet handles
When effort is applied to move the wheel, the axle turns a
_________________ distance, but moves with
__________________ force.
The _____________________ the wheel is when compared
to the axle, the _____________________ the mechanical
advantage.
Pulley
grooved wheel with a rope or chain running along the
groove
a ____________________________________
a load is attached to one end of the rope and a force is
applied to the other end
A pulley makes work easier by changing the direction of
the force and/or reducing the effort force.
Mechanical Advantage
equal to the number of ______________________
Fixed Pulley



MA = 1
does _______________ increase force
changes ________________ of force
 Movable Pulley



MA = 2
________________ force
does not change _______________
Pulley System/Block & Tackle




MA = 4
________________ of fixed and movable
pulleys
increases ________
may or may not change ______________