Download Teaching six simple machines to middle school students

Teaching six simple machines to middle
school students
Ingram School of Engineering
Bahram Asiabanpour, Ph.D., CMfgE
Jaime Hernandez, Ph.D.
Vasilis Vagias, Matthew Loerwald, Thomas Wilson
STELLAR II: Science and Technology for English Language Learners
Stellar summer institute, San Marcos, TX
th
8
TAKS
grade
exam sample
question
Definitions
Distance
Mass
Velocity
Acceleration
Force
Work
Distance
An increment that represents a finite change in
position. How far apart two objects are.
Mass
The mass of an object is
a fundamental property
of the object; a
numerical measure of its
inertia; a fundamental
measure of the amount
of matter in the object.
Mass can be measured in
many different ways and
can appear abstract. SI
units are recommended to
establish comfort.
Velocity
Velocity is concerned with the change in
position with respect to a change in time.
Acceleration
The rate of change of the velocity of a moving body
If you study a system and observe different velocities then
an acceleration (negative or positive) has taken place.
Force
Force is the product of
Mass and Acceleration
F =MxA
Measured in Newtons, a
well known force seen
daily is lbs (pounds) and is
the product of an
individuals mass multiplied
by 32 ft/s^2(acceleration
due to gravity)
Work
Work is the product of a force applied
over a distance.
W=Fxd
Understanding energy, forces, and motion
Six simple machines
Inclined
plane
Pulley
Wedge
Wheel
and axel
Screw
Levers
Simple Machines
Lever
Screw
Pulley
From these machines
all work can be made
easier in terms of force
exerted at the cost of
the distance moved.
Wheel
& Axle
There are really only
three simple machines
the other three are just
variations. Can you
guess which three are
they?
Simple
Machines
Inclined
Plane
Wedge
1- Inclined plane
• Definition: It is a flat surface whose endpoints are at
different heights.
• By moving an object up an inclined plane rather than
completely vertical, the amount of force required is
reduced, at the expense of increasing the distance the
object must travel.
1- Inclined plane
• Real world example: Ramps, Roads, Steps, etc.
1- Inclined plane
• In class experiment
1- Set up a plane as shown in below picture with 30 degrees angle and connect
a load.
2- Attached the spring scale to the other end and pull the load with it and read
the scale number.
3- Change the angle to 60 degrees and compare the new scale reading with the
previous one.
30 degrees
Recorded
force
60 degrees
2 - Lever
• Definition: A long rod or stick can be placed
on a point above ground known as a fulcrum
to lift an object that requires a large force with
a much smaller input force. There are first,
second and third class Levers
Fr x Lr = Fe x Le
2 - Lever
• Real World Example: Handles, Can Openers,
Seesaws, etc.
2 - Lever
• In class experiment
Materials: Ruler, pencil, and two masses
Directions: Set up materials as shown on
a flat surface.
1.
Use pencil as the fulcrum use spring
scale where the “effort” is applied
and measure force.
2.
Move pencil and repeat measurement
record new force.
3.
Validate Fr x Lr = Fe x Le
Position 1
L1=L2
Recorded
force
Position 2
6L1=4L2
3 - Pulley
Definition: A simple machine
consisting essentially of a wheel
with a grooved rim in which a
pulled rope or chain can run to
change the direction of the pull
and thereby lift a load
3 – Pulley
• Real World Examples: Flag Poles,
Dumbwaiters, etc.
3 - Pulley
• In Class Experiment
Materials: Two pulleys, rope or string, mass
hangers, and spring scale.
Directions:
1. Set up pulleys as shown in picture with one
suspended above ground.
2. Loop rope through second pulley and attach
mass hanger to the hook on the second
pulley (lower pulley).
3. Use the spring scale to measure the force
picking the load up by itself and again using
the pulley apparatus.
Recorded
force
Without
pulley
With pulley
4 - Wheel & Axel
Definition: a wheel and axel is a simple machine consisting of a large wheel
rigidly secured to a smaller wheel or shaft, called an axle. When either the wheel
or axle turns, the other part also turns. One full revolution of either part causes
one full revolution of the other part.
S1 X D1 = S2 X D2
where,
S1 = Input Speed S2 = Output Speed
D1 = Axle Diameter D2 = Wheel Diameter
4 – Wheel and Axel
• Real World Examples: Cars, Ferris wheels ,
wheelbarrows, etc.
4 – Wheel and Axel
• In class experiment
Materials: Mass hanger, rope, the small car, and spring scale.
Directions:
1.
Attach spring scale to rope and pull mass without the small car.
2.
Place mass on small car and pull with spring scale.
3.
Record results for all.
With
Recorded
force
Without
5 - Wedge
• A wedge is simply an
inclined plane turned on
its side. It follows the
same rules as Inclined
planes and can be
thought of as such.
Wedges are used as
either separating or
holding devices.
5 - Wedge
• Real World Examples: Axes, door stops,
chisels, etc.
Example: Cutting tool
A
B
26
6 - Screw
• A screw is simply a spiraled inclined plane. A screw can be
used to move objects side to side or up and down with ease.
Example
• Assume that you place a ruler parallel to a screw and count
10 threads in a distance of one inch. The pitch of the screw
would be 1/10.
• Since there are 10 threads per inch of screw, the distance
between two adjacent screw threads is 1/10 of an inch.
Also, remember that one complete revolution of a screw
will move the screw into an object a distance equal to the
pitch of the screw. Therefore, one complete revolution will
move a screw with 1/10 pitch a distance of 1/10 of an inch
into an object.
6- Screw
• Real World Examples, Screws and motors
• In actual applications, the screw is often turned by another
simple machine such as a lever or a wheel and axle. In this case,
the total mechanical advantage is equal to the circumference of
the simple machine to which the effort force is applied divided
by the pitch of the screw.
6 – Screw: In class experiment
• Use a screw with 12 threads per inch is turned by a screwdriver having a
handle with a diameter of 1 inch. The mechanical advantage would be
calculated as follows:
1- Determine the pitch of the screw: Pitch = 1/12 = .083
2- Determine the circumference of the handle of the screwdriver...
Circumference = 3.14 x diameter = 3.14 x 1 = 3.14 inches
3- Insert the values obtained into the formula and solve the equation:
Mechanical Advantage = Circumference/Pitch = 3.14 inches/0.083 = 37.83
Applications in Real World
• The union of simple
machines into complex
machines sparked the
industrial era and led
to the technological
boom we now live in.
They are simple but
highly effective
machines!
Conclusion
• When confronted with a cumbersome task
incorporate a simple machine to take the
“load” off
Relevant videos
• Screw and the wheel (4 minutes)
http://www.youtube.com/user/123peaceplease#p/u/10/v1hjiOp6FEU
• Lever (3 minutes)
http://www.youtube.com/user/123peaceplease#p/u/11/Us2KfO_yrPA
• Simple machines (6 minutes)
http://www.youtube.com/user/123peaceplease#p/u/13/grWIC9VsFY4
• Inclined plane (5 minutes)
http://www.youtube.com/user/123peaceplease#p/u/12/wWPiY6Of6-U
• Pulley
http://www.youtube.com/watch?v=9T7tGosXM58&feature=related
More Examples
• http://www.mikids.com/Smachines.htm
• Students project: Six simple machines (all in one)
http://www.youtube.com/watch?v=l1oCpWZk8pk