Feb. 9
Objectives:
• Determine AMA in pulley systems
• Determine efficiency in pulley systems
Bell Ringer:
1) Draw 6 pulley systems.
• In each pulley systems have a different number of supporting strings;
• Please draw neatly because unclear drawings are identified as "wrong."
• Plan must be rational (trace strings with your finger when done to make sure it "works.")
• Label E and R in each pulley system
• Name each pulley system
Lesson:
1) Students do "Bell Ringer" (see above); this may take 10 minutes or more depending on students... give them time to finish but not more than 20 minutes.
2) Review "number of supporting strings" and pulley names. (Show solutions to bell ringer by drawing them on board or having students draw them on the board!)
3) Announce: "Last class students made pulley systems with paper clips and string. Mr. Reimer said that he will give you opportunity in the next period to finish building pulley systems to show him. Today we will do work on paper since there is a substitute in class."
4) Review IMA, (Ideal Mechanical Advantage): "IMA = number of supporting strings" - since every supporting string shares part of the force load. Point out in bell ringer that number of supporting strings in each pulley system is also the IMA; see my notes for examples.
5) Teach students to determine AMA - see notes! Please do all the examples on the board. Students should copy down everything you do on the board into their science notebook or onto A4 paper to keep with them. If you have questions, two students who are very good at science are: Danny Kim, Jinni Kim(?), Audrey Ahn and Andy Yun. Those 4 students can answer your questions about any of these problems. In each AMA problem:
• identify pulley name, R and E
• identify number of supporting strings
• determine IMA
• calculate AMA
6) Teach students to determine "pulley efficiency" - see notes. Please do all the examples on the board. Students should copy down everything you do on the board into their science notebook or onto A4 paper to keep with them. In each efficiency problem:
• identify pulley name, R and E
• write down efficiency equation
• show all calculating work (see my examples in notes)
• record final answer as a percentage
• box your answer if it is not clear.
7) Distribute "Pulley AMA Efficiency" handout for student to complete in class and hand in.
8) Distribute "Pulley Calculate Draw" handout for student to complete in class and hand in.
Assignment:
1) Students complete "Pulleys AMA Efficiency handout" - due by end of class today.
2) Students complete "Pulleys Calculate Draw" - due next class.
