Work and PowerWork and Power

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Bellwork QuestionBellwork Question

What are the 6 topics on the What are the 6 topics on the 22ndnd semester survey semester survey assignment?assignment?

Reminder: Due on Thur. Reminder: Due on Thur. 1/9/141/9/14

Bellwork AnswerBellwork Answer

Astronomy & Gravitation Astronomy & Gravitation Matter Matter Heat Heat Sound & LightSound & Light Electricity & Magnetism Electricity & Magnetism Modern Physics Modern Physics

Work and PowerWork and Power

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Today’s AgendaToday’s Agenda

Background information on Background information on work and powerwork and power

Review and new equationsReview and new equations Work and Power LabWork and Power Lab

Fall Semester Carry-Fall Semester Carry-OverOver Metric prefixes and unitsMetric prefixes and units Conversions (dominoes)Conversions (dominoes) T-ChartsT-Charts Vectors vs. scalarsVectors vs. scalars Lab Variables (dependent, Lab Variables (dependent,

independent and controlled)independent and controlled) Forces (types of forces)Forces (types of forces) Several equationsSeveral equations

Background Background InformationInformation Work (scalar)Work (scalar): A force exerted : A force exerted

over a distance. over a distance.

Unit is joule (J)Unit is joule (J) Power (scalar):Power (scalar): The rate at The rate at

which work is done. which work is done.

Unit is watt (W)Unit is watt (W)

Work vs. PowerWork vs. Power

When lifting an object slowly When lifting an object slowly and quickly to the same and quickly to the same heightheight

Both have the same amount Both have the same amount of of workwork done done

Done Done slowlyslowly has has lessless powerpower Done Done quicklyquickly has has moremore powerpower

Review, Work and Review, Work and Power EquationsPower Equations Weight vs. Mass / Net ForceWeight vs. Mass / Net Force Distance, Velocity and Distance, Velocity and

AccelerationAcceleration WorkWork PowerPower

Work and Power LabWork and Power Lab

Objective:Objective:

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

Pre-Lab:Pre-Lab:

Using a domino, convert your Using a domino, convert your body weight into newtons.body weight into newtons.

(1 pound = 4.45 N)(1 pound = 4.45 N) EX: Aaron Gibson, EX: Aaron Gibson,

heaviest NFL player, heaviest NFL player,

max weight 410 lbmax weight 410 lb

HypothesisHypothesis: : (Answer the (Answer the questions in complete questions in complete sentences)sentences)

1.1. Do you think physical Do you think physical exercises will produce exercises will produce powers greater or smaller powers greater or smaller then a light-bulb?then a light-bulb?

2.2. Do you think physical Do you think physical exercises will produce exercises will produce powers greater or smaller powers greater or smaller then a lawn mower engine?then a lawn mower engine?

Materials:Materials:

Meter stickMeter stick StopwatchStopwatch Books or other weightsBooks or other weights

(Return all materials to the cart (Return all materials to the cart up front when finished)up front when finished)

Exercise Data Table:

Exercise # of Reps

Distance (m)

Time (s)

Weight (N)

Work in 1 Rep. (J)

Total Work (J)

Power (W)

               

               

               

               

ProceduresProcedures::Record your own Record your own exercises!exercises!

1.1. Choose an exercise that involves doing Choose an exercise that involves doing work against the force of gravity. work against the force of gravity.

2.2. Measure the distance that you exerted Measure the distance that you exerted the force and record in a data table.the force and record in a data table.

3.3. Now, perform several repetitions (5 or Now, perform several repetitions (5 or 10) of the exercise as fast as you can. 10) of the exercise as fast as you can. Have your lab partner(s) count the Have your lab partner(s) count the repetitions and measure the total time repetitions and measure the total time it takes. it takes.

4.4. Repeat for three more exercises. Use Repeat for three more exercises. Use two exercises that use arm muscles, two exercises that use arm muscles, and two exercises that use leg and two exercises that use leg muscles.muscles.

Examples of ExercisesExamples of Exercises

Name of exercise – force of gravityName of exercise – force of gravity lifting an object (arm) – object weightlifting an object (arm) – object weight raising on toes (leg) – full body weightraising on toes (leg) – full body weight arm curls (arm) – object weightarm curls (arm) – object weight knee bends (leg) – full body weightknee bends (leg) – full body weight push-ups (arm) – half body weightpush-ups (arm) – half body weight vertical jump (leg) – full body weightvertical jump (leg) – full body weight etc.etc.

(1 lb. = 4.45 N)(1 lb. = 4.45 N)Book = 3.3 lb. & Weight = 2.5 Book = 3.3 lb. & Weight = 2.5 lb. lb.

Reminder of units!Reminder of units!

All distances need to be in All distances need to be in metersmeters

You will need the weights in You will need the weights in newtons for this activity.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 Please leave the rulers on your

desk, thanks.desk, thanks.

Work and Power Lab Work and Power Lab (Day 2)(Day 2)

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Bellwork Bellwork

What is work?What is work? A force exerted over a A force exerted over a

distance.distance. Fill out the student rubric and Fill out the student rubric and

staple it to the top of the labstaple it to the top of the lab

Today’s AgendaToday’s Agenda

Finish “Work and Power Lab”Finish “Work and Power Lab” Work on 2Work on 2ndnd Semester Survey Semester Survey

AssignmentAssignment

CalculationsCalculations: - Show the : - Show the work for 1 exercise (3 T-work for 1 exercise (3 T-Charts)Charts)1.1. Calculate the work done in one Calculate the work done in one

repetition for each exercise. repetition for each exercise. ( W ( W11 = F · d ) = F · d )

2.2. Calculate the total work done Calculate the total work done for each exercise. for each exercise. ( W ( Wtotaltotal = W = W11 × [# of reps] ) × [# of reps] )

3.3. Calculate the power done for Calculate the power done for each exercise. ( P = Weach exercise. ( P = Wtotaltotal / t ) / t )

ConclusionConclusion:: (In complete (In complete

sentences)sentences) 1.1. How does the power output of your arm How does the power output of your arm muscles compare to the power output of your muscles compare to the power output of your leg muscles? Why do you think this is? leg muscles? Why do you think this is?

2.2. How does your power output compare to the How does your power output compare to the power output of a 18 watt fluorescent bulb? power output of a 18 watt fluorescent bulb?

3.3. How does your power output compare to the How does your power output compare to the power output of a lawn mower engine? (about power output of a lawn mower engine? (about 750 watts)? 750 watts)?

4.4. Is the power output of your muscles more or Is the power output of your muscles more or less than you thought it would be? less than you thought it would be? (Hypothesis)(Hypothesis)

5.5. Did the activity that used the largest force Did the activity that used the largest force result in the largest power produced? result in the largest power produced?

6.6. Explain how a large force can result in Explain how a large force can result in relatively small power.relatively small power.

7.7. What is the relationship between work and What is the relationship between work and power?power?

8.8. What is the relationship between mass and What is the relationship between mass and weight?weight?