Transcript Slide 1

GK-12 Lesson Planning
8th Grade Science / Engineering
Simple Machines
An Activity Series
Aida Peterson (Teacher)
Matthew Silbernagel (Fellow)
Outline
• Physical Science: Goals, Standards, &
Benchmarks (CDE)
• Introduction: Work & Simple Machines
• Hands-on Investigations
–
–
–
–
Lever
Pulley
Inclined Plane, Screw, Wedge
Wheel & Axle
• Assessment
• Alternative Approaches / Adaptations
A.P. / M.S. GK-12
2
Goals
• Define and give examples of “work” and
“machine”
• Identify simple machines (i.e., inclined
plane, screw, lever, wheel & axle, wedge,
and pulley
• Quantify work and mechanical advantage
• Classify simple and compound machines
3
Standards
8.1 Students understand the processes
of scientific investigation and design,
conduct, communicate about, and
evaluate such investigations.
8.2 Physical Science: Students know and
understand common properties, forms,
and changes in energy. (Focus: Physics
and Chemistry)
Source: CDE
4
Benchmarks (1)
1.1 Scientific Investigation
• Using examples to demonstrate that scientific ideas are used
to explain previous observations and to predict future events
• Using appropriate tools, technologies, and measurement units
to gather and organize data
• Interpreting and evaluating data in order to formulate
conclusions
• Communicating results of their investigations in appropriate
ways (for example, written reports, graphic displays, oral
presentations)
• Using metric units in measuring, calculating, and reporting
results
• Explaining that scientific investigations sometimes result in
unexpected findings that lead to new questions and more
investigations
5
Source: CDE
Benchmarks (2)
2.3 Students understand that interactions can produce
changes in a system, although the total quantities of
matter and energy remain unchanged.
• Identifying and classifying factors causing change within a
system (for example, force, light, heat)
• Identifying and predicting what will change and what will
remain unchanged when matter experiences an external force
or energy change (for example, boiling a liquid; comparing the
force, distance, and work involved in simple machines)
• Describing, measuring (for example, time, distance, mass,
force) and calculating quantities that characterize moving
objects and their interactions within a system (for example,
force, velocity, acceleration, potential energy, kinetic energy)
Source: CDE
6
Simple Machines (Review)
• Define “work” and “simple machine”
• Identify simple machines
–
–
–
–
–
–
inclined plane
screw
wedge
lever
wheel & axle
pulley
7
Materials
•
•
•
•
•
•
paint can
paint stick
book
spring scale
meter stick
string
•
•
•
•
•
•
several pulleys
toy car (weighted)
three boards (same length)
three boards (different length)
long pole (ring stand)
milk carton
8
Lever – Activity Station
They multiply the effort force
and change its direction.
Mechanical Advantage is
usually greater than one if the
fulcrum is closer to the
resistance force than the
effort force.
9
Pulleys – Activity Station
Fixed vs.
Movable
Pulleys
10
Inclined Plane, Screw, & Wedge
– Activity Station
Advantage – less effort force
Disadvantage – more effort
distance
The mechanical advantage
(M.A.) is the length (Effort
distance) divided by the height
(Resistance distance ).
M.A. = dE / dR.
Can the advantage be less than 1 (M.A.<1?)
Inclined Plane
11
Wheel and Axle – Activity Station
The wheel/axle
combination is just
a lever that rotates
in a circle!
If effort force is applied to the wheel,
effort force is multiplied because the
wheel moves a greater distance
than the axle. The mechanical
advantage is greater than one.
M.A. = radius of wheel / radius of
axle.
If effort force is applied to the axle,
the mechanical advantage is less
than one.
M.A. = radius of axle / radius of
wheel.
12
Assessment
• Verbal Interaction:
– Initial class survey
– Table/Individual inquiries
– Identifications with team competitions
• Written responses:
– Quantitative analysis
– “What if” questions
– Applications (open-ended)
13
Alternative Approaches &
Adaptations
• Research body parts (biomechanics),
construction equipment, or household objects
that are used as simple machines
• Efficiency: eff = Wo / Wi x 100%
• References on work and simple machines
– http://www.avon.k12.ct.us/avonhigh/Academics/Departments/Science/Physics/Si
mpleMachine.htm
– http://www.iit.edu/~smile/ph9005.html
– http://www.cfaitc.org/LessonPlans/pdf/109.pdf
• Interactive websites (?)
– http://mws.mcallen.isd.tenet.edu/mchi/ipc/ch15htm/ch15sec4.htm
14
Questions / Comments ?
15
Backup slides
Work and Simple Machines
Objectives:
The student will be able to:
1) Define and give examples of "work" and "machine"
2) Identify simple machines (inclined plane, screw, lever,
wheel and axle, wedge, and pulley)
3) Classify simple and compound machines
4) Name body parts that can be used as simple machines
Materials:
paint can, book, spring scale, meter stick, string, milk carton, several pulleys, toy car-weighted, three boards-same length, three boards-different length, long pole
Strategy:
Work and Simple Machines
Have several students attempt to open an empty paint can with their hands or attempt
to move a heavy desk. Have the students determine that although force was used, the
objects did not move a distance and there was no motion; thus, no work was done since
work is equal to force times distance.
Then have a student open the paint can by using something to pry off the top of the
can. Explain that the object was used as a lever, one kind of simple machine, and that a
machine is something that makes work easier to do.
Also help the students discover that two or more simple machines can be used together to
make compound machines.
Activity-Lever
Tie a book to one end of a meter stick. Use a milk carton weighted with dirt or sand
as the fulcrum, the point on which the stick rests or turns. Set the fulcrum at the 15 cm
mark. On a chart, record where the fulcrum was set, the load arm length, and the force
arm length. Use the end of the spring scale to pull down the end of the meter stick and
record the force shown on the scale.
Repeat the steps above for 20 cm, 25 cm, 30 cm, and 35 cm. Discuss the placement of
the fulcrum in relation to the placement of the load and the amount of force needed to lift
the load.
Question:
Is the direction the load moves and the direction of the force the same?
16