Download Simple Machines

Simple Machines
Types of Simple Machines
A simple machine does work with only one
movement. Simple machines can be combined to form more
complex machines
We tend to think of
machines as motorized
devices with many
moving parts. In
physics, a machine can
be a simple item, like a
shovel or a screw top lid
Overview of the 6 Simple Machines
1.
2.
3.
4.
5.
6.
Lever ____
Pulley ____
Wheel & Axle ____
Inclined Plane ____
Screw _____
Wedge ____
Match the tool...
A.
B.
C.
D.
E.
F.
Knife
Crowbar
Pencil Sharpener
Elevator
Wheelchair ramp
Lid to a jar
Levers
---- A bar that is free to pivot or turn at a fixed point.
--- The fixed point is called the FULCRUM
--- The output force produced depends on the length of the
arm
Types of Levers
1st Class Lever
Fulcrum is located between the
input and output forces
Examples:
Crowbar
Seesaw
Scissors are two class 1 levers
2nd Class Lever
Effort and fulcrum are on
opposite sides, load is
between them
Examples:
Wheelbarrow
Bottle opener
3rd Class Levers
Effort is applied between the
fulcrum and the load
Ex. Baseball bat, tweezers,
fishing pole
Levers (3 Classes)
Which class is a:
1.
2.
3.
4.
5.
6.
6.
Hammer ___
Wheelbarrow ___
Scissors ____
The claw of a hammer ___
Refrigerator door ____
Shovel ____
Baseball bat ____
MEMORY TRICK
*remember the word FLEx*
1. F = fulcrum in the middle
2. L = load is in the middle
3. E = effort is in the middle
x is just for fun
Ideal Mechanical Advantage of a Lever
IMA = Length of the input arm
Length of the output arm
What is the IMA of the lever shown below? ________
If the output arm
was only 15 m, what
is the IMA of the
lever? _____
As you shorten the output arm,the mechanical
advantage is [ increased / decreased ]
Lever Animations
at http://www.technologystudent.com/forcmom/lever1.htm
What is a pulley?
1. Consists of a wheel and a rope
(chain)
2. A fixed pulley is actually a modified
first class lever. It is fixed because
part of it is attached and doesn't move.
Ex. Elevators, dumb waiters,
flagpoles
3. Moveable pulleys multiply force
The Block and Tackle
System of pulleys consisting of fixed
and movable pulleys.
Basically the weight of the object is
spread over multiple ropes, meaning
less force needs to be applied to raise
it.
Essentially the rope is longer, and you
must pull it a longer distance to raise
the object. Work = force x distance
How Stuff Works has an excellent
explanation of this.
Multiple Pulleys Increase Mechanical Advantage
By spreading the
force over a greater
distance (using more
than one pulley) you
will reduce the effort
required to raise an
object.
In each case, the length of the
rope gets longer, and the effort
required to lift the block gets
smaller
1 pulley = 100 N
2 pulleys = 50 N
3 pulleys = 25 N
Check for Understanding
1. Which design will give
you the greatest
mechanical advantage?
2. If F1 = 100 N, what is
F2?
3. Identify
the movable and fixed
pulleys in each design.
What is a Wheel and Axle?
Shaft or axle attached to a larger wheel
Examples: door knobs, screwdrivers, faucet handles, pencil
sharpener
Mechanical Advantage of Wheel and Axle
IMA = radius of wheel
radius of axle
You can increase the advantage by using a larger wheel
Gears = multiple wheels that interlock
together, one turn of a larger wheel causes
the smaller wheel to turn multiple times
In which figure(s) will the F
rotate clockwise? _______
Inclined Planes - a sloping
surface, such as a ramp, that
reduces the amount of force
required to do work
Like all machines, the principle
is to spread the Force out over
a longer Distance.
Ideal Mechanical Advantage
IMA = length of slope
height of slope
Walking up the hill in a
zigzag will require less
effort than walking straight
up the hill.
Which of the following designs
will produce the greater
mechanical advantage?
IMA = length of slope
height of slope
http://youtu.be/suDJARX0nMA
1. Energy and work are measured in ____________
2. For exertion, the greater the distance,
the [ greater / lesser ] the force required.
3. The "sloping flat thing" is actually the
____________________
1. What is the pivot point of the teeter totter called? ________
2. If you double the distance, you can _______ the forced
needed.
3. Archimedes said: "give me a _______________ and I will
move the _____________
1. The lever gave Professor B a mechanical _____________
2. Mechanical Advantage = output divided by ___________
3. The inclined plane is less efficient due to the force of
_____________
The Screw - an inclined
plane wrapped in a spiral
around a post
Examples: bolts, screws,
lids, spiral staircase
The Wedge - an inclined plane
with two sides
Examples: Axes, knives,
chisels
QUIZ TIME!
1. What type of machine is a wheelchair ramp?
2. What type of machine is a crowbar?
3. The fixed point for a lever to pivot is the _______.
4. If the LOAD is in the middle of a lever, it is called a
[1st, 2nd, 3rd ] class lever.
5. What type of lever is pictured?
[ 1st, 2nd, or 3rd class ]
6. A system of pulleys that reduces the force needed to lift an
object is called a ________________________
7. Give an example of a wheel and axle: ____________
8. How can you increase the mechanical advantage of a wheel
and axle?
9. A ________ consists of multiple wheels that interlock
10. What reduces the efficiency of an inclined plane? _____
11. A wedge is an _____________________ with two sides.