Work and PowerWork and Power

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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 WorkWork PowerPower

Work and Power LabWork and Power Lab

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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

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:

Convert your body weight into Convert your body weight into newtons.newtons.

(1 pound = 4.45 N)(1 pound = 4.45 N) EX 1: Vince Wilfork, EX 1: Vince Wilfork,

NE Patriots player, NE Patriots player,

weight 325 lb.weight 325 lb.

Pre-Lab:Pre-Lab:

EX 2: House cat of 8.6 lb. EX 2: House cat of 8.6 lb.

HypothesisHypothesis: : (Write out the question and (Write out the question and answer in complete answer in complete sentences.)sentences.) Do you think physical exercises Do you think physical exercises

for for armsarms and and legslegs will produce will produce powers on the order of what?powers on the order of what?

(list is on the next slide)(list is on the next slide)

cell phone charger (2 W)cell phone charger (2 W) clock radio (7 W)clock radio (7 W) light-bulb (15 W)light-bulb (15 W) laptop computer (50 W)laptop computer (50 W) game system (100 W)game system (100 W) TV (300 W)TV (300 W) refrigerator (600 W)refrigerator (600 W) microwave oven (900 W) microwave oven (900 W) AC Unit (1500 W)AC Unit (1500 W) electric stove/oven (3000 W)electric stove/oven (3000 W) electric clothes dryer (5000 W)electric clothes dryer (5000 W)

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. Book = 3.3 lb.

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

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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. (1 pound = 4.45 newtons)(1 pound = 4.45 newtons)

CalculationsCalculations: - Show the : - Show the work for each exercisework for each exercise

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 the 3(In the 3rdrd person person

and paragraph form)and paragraph form) What was the range of powers for the What was the range of powers for the armarm

exercises? exercises? If you could transfer this If you could transfer this armarm power to electric power to electric

power, what would it be able to power? power, what would it be able to power? What was the range of powers for the What was the range of powers for the legleg

exercises?exercises? If you could transfer this If you could transfer this legleg power to electric power to electric

power, what would it be able to power? power, what would it be able to power? Is the power output of your arm muscles more Is the power output of your arm muscles more

or less than you thought it would be? or less than you thought it would be? (Hypothesis)(Hypothesis)

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

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

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

cell phone charger (2 W)cell phone charger (2 W) clock radio (7 W)clock radio (7 W) light-bulb (15 W)light-bulb (15 W) laptop computer (50 W)laptop computer (50 W) game system (100 W)game system (100 W) TV (300 W)TV (300 W) refrigerator (600 W)refrigerator (600 W) microwave oven (900 W) microwave oven (900 W) AC Unit (1500 W)AC Unit (1500 W) electric stove/oven (3000 W)electric stove/oven (3000 W) electric clothes dryer (5000 W)electric clothes dryer (5000 W)

Make-up Data

Exercises (5 Reps for each exercise)

• Arm curls• Push ups• Jumping jacks• Knee bendsDistances• Arm curl = 43 cm• Push up = 19 cm• Jumping jack = 1.5 cm• Knee bend = 32 cm• * Covert cm to m *

Time for five reps• Arm curls = 3.25 s• Push ups = 5.13 s• Jumping jacks = 6.79 s• Knee bends = 4.83 sFind the force of gravity (weight)

in Newtons• Weight = 2.5 pounds (arm

curls)• Your weight (for all the other

exercises and ½ you weight for push ups)

• (1 pound = 4.45 Newtons)

Grading Rubric

• Title (2)• Objective (3)• Pre-Lab (5)• Hypothesis (5)• Materials (2)• Data (5) • Conversions (5)• T-Charts (12)• Conclusion (16)• Order (5)• Total = 60