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Feb. 16

Objectives: 

• Each student should pass the test!

Bell Ringer: 

None-TEST DAY

Lesson: 

1) Take the test

Assignment: 

Enjoy a break from school!

Feb. 16

Objectives: 

• Each student should complete building a block and tackle pulley with correct number of assigned strings (ex. "four") and effort in correct direction (ex. "up")

• Each student should measure effort force and resistance force in a pulley, then determine IMA, AMA and efficiency.

Bell Ringer: 

We have a compound pulley with three supporting strings and effort pulling down.  The resistance is 250 N, the effort is 90 N, the resistance moves up 3 m:

1. Draw this pulley system

2. Determine IMA for this pulley system

3. Determine the AMA for this pulley

4. Determine the efficiency for this pulley

Lesson: 

1) Students each make a 3 string pulley with effort pulling up.

     • Attach 300 g mass to pulley

     • Draw diagram on A4 paper.

     • Determine: effort, IMA, AMA, efficiency.

     • Show all measurements and ALL CALCULATIONS on your paper.

2) Repeat same exercise with effort pulling down.

3) Submit assignment before end of class.

Assignment: 

1) Complete post-unit reflection and review.  Bring completed reflection hand-written or printed in hard copy next period.  

2) Bring reflection rubric stapled to top of your reflection with your assessment of your own work completed.

Feb. 11

Objectives: 

• Students will be able to determine AMA and efficiency in pulley systems

• Students will be able to draw pulley diagrams with correct number of supporting ropes.

Bell Ringer: 

1) Draw a pulley system with an IMA of 3 and effort pulling up.

2) Draw a pulley system in which the effort moves 4 times farther than the resistance.

3) What is the efficiency in a pulley system if you pull 5 m with 5 N of force and this lifts a 20 N resistance a vertical distance of 1 m?

Lesson: 

1) Review last days pulley worksheet:  Pulleys; Calculate & Draw.

2) Collect worksheets from students

3) Review summative breakdown for this unit: 

     50% trebuchet:

          • 10% drawing of trebuchet model; (due Monday, Feb 16)

          • 30% trebuchet demonstration;  (due Thursday, Feb 12)

          • 10% reflection  (due Wednesday, Feb 18)

     50% paper test.  (on Thursday, Feb 19)

Assignment: 

1) Download and complete AMA Efficiency 2.

Feb. 5

Objectives: 

• Identify, name and build three different kinds of pulley systems

• Determine IMA in pulley systems

Bell Ringer: 

1) For each of three types of pulleys:

     (a) diagram the pulley system

     (b) name the pulley system

     (c) label R and E on your diagram

     (d) determine IMA for each of your pulley systems

Lesson: 

1) Students take quiz on work, torque and all lever topics up to, but not including, pulleys.

2) Students build 3 types of pulleys - fixed, moveable, and block and tackle (or compound pulley) - using paper clips as pulleys (or plastic pulleys if they are available).  This is individual student performance assessment so students do all work themselves.

3) Time remained in class so that each student was additionally assigned to build "block & tackle" having (i) three supporting strings with effort pulling down and (ii) three supporting strings with effort pulling up.

Assignment: 

1) Complete trebuchet (due in one week!) 

Feb. 2

Objectives: 

• Identify lever in common household objects.

• Describe different levers for theid advantage.

• Determine E, R, etc. in different lever systems.

Bell Ringer: 

Diagram a lever with:

     R = 5 kg,

     E = 1.5 kg,

     E = 2.8 m from fulcrum.

1.  Diagram

2. Calculate IMA (show calculaltions)

3. Determine distance of R from fuclrum (show calculations)

Lesson: 

1) Show a normal lever; reverse R and fulcrum (to make 2nd class lever) and ask students if this is still a lever.  Discuss why it is or is not.

2) Show students tweezers (or tongs) and discuss how this is a lever and where the effort, resistance, fulcrum, etc. are.  Identify this as a "Class III" lever.

3) Repeat demonstration and discussion for for garlic press; identify this as a "Class III" lever.

4) Discuss uses of each type of lever (ie. what advantage does a class 3 lever give the user?)

5) See Brainpop "Levers" for description of kind of levers at: this link.

6) Distribute "Kinds of Levers" worksheet. 

Assignment: 

1) Complete "Kinds of Levers" worksheet.  Due next class (all).

Jan. 22

Objectives: 

• formalize required notation: τ(tau) =torque, w=work, f=force (N, lb., kg, etc.) , d=distance (m, cm, ft., etc.) 

• determine ideal mechanical advantage (IMA) of lever systems

Bell Ringer: 

Seesaw’s are found on the playground and always have the fulcrum in the middle of the seesaw.  In these questions all of the people are identical mass.  Draw a seesaw with the appropriate number of people in the appropriate locations to answer the questions below.  In these questions all of the people are identical mass.

1) Draw a seesaw showing two people which balance each other.

2) Find and draw two unique arrangements in which a seesaw showing three people which balance each other; no one can be on the fulcrum.

3) Find and draw two unique arrangements in which a seesaw carrying 4 people is balanced; no one can be on the fulcrum.

Lesson: 

1) Return quiz; discuss questions students did wrong and how to correct them (re-do quiz as homework?)

2) See <http://science.howstuffworks.com/pulley1.htm> fro a description of force/distance tadeoffs.

3) Teach IMA = big force/small force or big distance/small distance, etc.

4) Complete "Mechanical Advantage" worksheet.

Assignment: 

1) Draw your trebuchet plan; due next class: 

(a) draw on A4 graph paper or A4 blank, printer paper

Jan. 19

Objectives: 

• Know and articulate the difference between work and torque.

• Measure and calculate torque in a lever system.

• Provide description of summative project requirements (specifications)

Bell Ringer: 

(1) If you lifted a 412g shoe a distance of 3.7 cm with 150 g, how far did the 150 g mass move? 

(2) What are two requirements for an event to be "work?"

(3) Describe one thing you do which is not work.

Lesson: 

Summative Project

1) Distribute guidelines for trebuchet summative project. Discuss project with students; outline your requirements.  Emphasize "no elastic launchers!" (This took 30 minutes!)

Lever Sense

2) Discuss affect of moving fulcrum on "what happens to the lever." Conversely, show how to balance an unbalanced lever by moving masses without moving the fulcrum.  This is to help students develop a "Lever Sense."

Torque intro

3) Review procedure for using a balance to measure the mass of a students shoe with the "work" equation.  Remind students that the difficulty was (i) measuring center of mass for shoe while it was sitting on the meter stick and (ii) measuring the distance the weight and shoe travelled up or down.

4) Demonstrate how moving the shoe farther from fulcrum makes it act heavier; point out: (i) mass of shoe is same (ii) but force of shoe is greater.

5) Explain that as shoe is moved farther from the fulcrum it seems to apply "more" force to lever EVEN WHILE LEVER IS NOT MOVING!

6) This affect is torque.  Torque is created by force (the shoe) and how far the shoe is from the fulcrum.  This is different than work; work depends on how far shoe moves; torque depends on how far the shoe is from the fulcrum.  w = fd and t = fd; however, in work situation distance is parallel to force applied; in torque situation, the distance is perpendicular to force applied.

7) Discuss examples in which torque changes (ex. cheater bar on lug nut wrench, longer pry bar, opening door by pushing on handle instead of close to hinge, etc.)

Torque Practice

8) Students weigh their shoe using "torque" calculation in class (instead of work); have students hang shoe an weight by string so that distance is clearer to measure to improve accuracy .

Assignment: 

1) Complete "Lever Sense" handout [I also distributed "Torque" handout but did not have time to instruct or complete it.]

Objectives: 

• Calculate work, force and distance given the other two parts of the equation.

• Uses units with every measurement.

• Name and identify several different units of force, several different units of distance and several different units of work (discriminate between mass & force)

• Levers as example of system in machines.  (see Bill Nye-Simple Machines)

• Identify parts of lever system (compare to math “functions;” input, output, operation, parts)

• Determine missing measurement when provided with other three measurements in lever system by calculating work=force x distance; work in = work out.

Bell Ringer: 

(1) If you had 30 Newtons of force moving a box 3 meters, how much work would that be? 

(2) Are there some ways we do the same work with less effort?  Explain. 

Lesson:

1. Collect Parent sign form & “Work” worksheet.

2. Demonstrate lever and show how the work in equals the work out (teeter-totter type lever is good example.)  

3. Show “Bill Nye” simple machines movie (very general and broad introduction based on “work.”

4. Discuss: why do we use machines if they do not reduce the “work?”

5. Introduce Levers:

(a) Draw lever system (compare to mathematical function: input, output, etc.)

(b) Identify parts of lever (fulcrum, lever, effort/force/input, resistance/force/output.)

(c) Solve one or two lever examples on board.

Assignment: 

Complete “Intro to Levers” worksheet.