GK-12 Lesson Planning8th Grade Science / Engineering

Simple MachinesAn Activity Series

Aida Peterson (Teacher)

Matthew Silbernagel (Fellow)

A.P. / M.S. GK-12 2

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

3

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

4

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

5

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

Source: CDE

6

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

7

Simple Machines (Review)

• Define “work” and “simple machine”

• Identify simple machines– inclined plane– screw– wedge– lever– wheel & axle– pulley

8

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

9

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.

10

Pulleys – Activity Station

Fixed vs. Movable Pulleys

11

Inclined Plane, Screw, & Wedge – Activity Station

Inclined Plane

Advantage – less effort forceDisadvantage – 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?)

12

Wheel and Axle – Activity StationThe 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.

13

Assessment

• Verbal Interaction:– Initial class survey– Table/Individual inquiries– Identifications with team competitions

• Written responses:– Quantitative analysis– “What if” questions– Applications (open-ended)

14

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

15

Questions / Comments ?

16

Backup slidesWork 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?