1. Work and Power 1/7/14

2. Bellwork Question What are the 6 topics on the 2 nd semester survey assignment? What are the 6 topics on the 2 nd semester survey assignment? Reminder: Due on Thur. 1/9/14 Reminder: Due on Thur. 1/9/14

3. Bellwork Answer Astronomy & Gravitation Astronomy & Gravitation Matter Matter Heat Heat Sound & Light Sound & Light Electricity & Magnetism Electricity & Magnetism Modern Physics Modern Physics

4. Work and Power 1/7/14

5. Today’s Agenda Background information on work and power Background information on work and power Review and new equations Review and new equations Work and Power Lab Work and Power Lab

6. Fall Semester Carry-Over Metric prefixes and units Metric prefixes and units Conversions (dominoes) Conversions (dominoes) T-Charts T-Charts Vectors vs. scalars Vectors vs. scalars Lab Variables (dependent, independent and controlled) Lab Variables (dependent, independent and controlled) Forces (types of forces) Forces (types of forces) Several equations Several equations

7. Background Information Work (scalar): A force exerted over a distance. Work (scalar): A force exerted over a distance. Unit is joule (J) Power (scalar): The rate at which work is done. Power (scalar): The rate at which work is done. Unit is watt (W)

8. Work vs. Power When lifting an object slowly and quickly to the same height When lifting an object slowly and quickly to the same height Both have the same amount of work done Both have the same amount of work done Done slowly has less power Done slowly has less power Done quickly has more power Done quickly has more power

9. Review, Work and Power Equations Weight vs. Mass / Net Force Weight vs. Mass / Net Force Distance, Velocity and Acceleration Distance, Velocity and Acceleration Work Work Power Power

10. Work and Power Lab

11. Objective: To determine how much work and power is done in physical exercises. To determine how much work and power is done in physical exercises.

12. Pre-Lab: Using a domino, convert your body weight into newtons. Using a domino, convert your body weight into newtons. (1 pound = 4.45 N) (1 pound = 4.45 N) EX: Aaron Gibson, EX: Aaron Gibson, heaviest NFL player, max weight 410 lb

13. Hypothesis: (Answer the questions in complete sentences) 1.Do you think physical exercises will produce powers greater or smaller then a light-bulb? 2.Do you think physical exercises will produce powers greater or smaller then a lawn mower engine?

14. Materials: Meter stick Meter stick Stopwatch Stopwatch Books or other weights Books or other weights (Return all materials to the cart up front when finished)

15. Exercise Data Table: Exercise# of Reps Distance (m) Time (s) Weight (N) Work in 1 Rep. (J) Total Work (J) Power (W)

16. Procedures: Record your own exercises! 1.Choose an exercise that involves doing work against the force of gravity. 2.Measure the distance that you exerted the force and record in a data table. 3.Now, perform several repetitions (5 or 10) of the exercise as fast as you can. Have your lab partner(s) count the repetitions and measure the total time it takes. 4.Repeat for three more exercises. Use two exercises that use arm muscles, and two exercises that use leg muscles.

17. Examples of Exercises Name of exercise – force of gravity Name of exercise – force of gravity lifting an object (arm) – object weight lifting an object (arm) – object weight raising on toes (leg) – full body weight raising on toes (leg) – full body weight arm curls (arm) – object weight arm curls (arm) – object weight knee bends (leg) – full body weight knee bends (leg) – full body weight push-ups (arm) – half body weight push-ups (arm) – half body weight vertical jump (leg) – full body weight vertical jump (leg) – full body weight etc. etc. (1 lb. = 4.45 N) (1 lb. = 4.45 N) Book = 3.3 lb. & Weight = 2.5 lb.

18. Reminder of units! All distances need to be in meters All distances need to be in meters You will need the weights in newtons for this activity. You will need the weights in newtons for this activity. Book = 3.3 lb. Book = 3.3 lb. Round weight = 2.5 lb. Round weight = 2.5 lb. (1 pound = 4.45 newtons) (1 pound = 4.45 newtons) Please leave the rulers on your desk, thanks. Please leave the rulers on your desk, thanks.

19. Work and Power Lab (Day 2) 1/8/14

20. Bellwork What is work? What is work? A force exerted over a distance. A force exerted over a distance. Fill out the student rubric and staple it to the top of the lab Fill out the student rubric and staple it to the top of the lab

21. Today’s Agenda Finish “Work and Power Lab” Finish “Work and Power Lab” Work on 2 nd Semester Survey Assignment Work on 2 nd Semester Survey Assignment

22. Calculations: - Show the work for 1 exercise (3 T-Charts) 1.Calculate the work done in one repetition for each exercise. ( W 1 = F · d ) 2.Calculate the total work done for each exercise. ( W total = W 1 × [# of reps] ) 3.Calculate the power done for each exercise. ( P = W total / t )

23. Conclusion: (In complete sentences) 1.How does the power output of your arm muscles compare to the power output of your leg muscles? Why do you think this is? 2.How does your power output compare to the power output of a 18 watt fluorescent bulb? 3.How does your power output compare to the power output of a lawn mower engine? (about 750 watts)? 4.Is the power output of your muscles more or less than you thought it would be? (Hypothesis) 5.Did the activity that used the largest force result in the largest power produced? 6.Explain how a large force can result in relatively small power. 7.What is the relationship between work and power? 8.What is the relationship between mass and weight?