Transcript Power and Work Activity

Work and Power
1/29/15
Background Information
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Work (scalar): A force exerted
over a distance.
Unit is joule (J)
Power (scalar): The rate at which
work is done.
Unit is watt (W)
Work vs. Power
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When lifting an object slowly and
quickly to the same height
Both have the same amount of
work done
Done slowly has less power
Done quickly has more power
Review, Work and Power
Equations
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Weight vs. Mass / Net Force
Work
Power
Work and Power Lab
1/30/15
Review, Work and Power
Equations
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Weight vs. Mass / Net Force
Distance, Velocity and
Acceleration
Work
Power
Objective:
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To determine how much work and
power is done in physical
exercises.
Pre-Lab:
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Convert your body weight into
newtons.
(1 pound = 4.45 N)
EX 1: Vince Wilfork,
NE Patriots player,
weight 325 lb.
Pre-Lab:
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EX 2: House cat of 8.6 lb.
Hypothesis:
(Write out the question and
answer in complete sentences.)
Do you think physical exercises for
arms and legs will produce powers
on the order of what?
(list is on the next slide)
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cell phone charger (2 W)
clock radio (7 W)
light-bulb (15 W)
laptop computer (50 W)
game system (100 W)
TV (300 W)
refrigerator (600 W)
microwave oven (900 W)
AC Unit (1500 W)
electric stove/oven (3000 W)
electric clothes dryer (5000 W)
Materials:
Meter stick
 Stopwatch
 Books or other weights
(Return all materials to the cart up
front when finished)
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Exercise Data Table:
Exercise
# of Distance Time Weight Work in Total
Reps (m)
(s)
(N)
1 Rep.
Work
(J)
(J)
Power
(W)
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.
Examples of Exercises
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Name of exercise – force of gravity
lifting an object (arm) – object weight
raising on toes (leg) – full body weight
arm curls (arm) – object weight
knee bends (leg) – full body weight
push-ups (arm) – half body weight
vertical jump (leg) – full body weight
etc.
(1 lb. = 4.45 N)
Book = 3.3 lb.
Work and Power Lab
(Day 2)
2/4/15
Reminder of units!
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All distances need to be in meters
You will need the weights in
newtons for this activity.
Book = 3.3 lb.
(1 pound = 4.45 newtons)
Calculations: - Show the work
for each exercise
1. Calculate the work done in one
repetition for each exercise.
( W1 = F · d )
2. Calculate the total work done for
each exercise.
( Wtotal = W1 × [# of reps] )
3. Calculate the power done for
each exercise. ( P = Wtotal / t )
Conclusion: (In the 3rd person and
paragraph form)
 What was the range of powers for the arm
exercises?
 If you could transfer this arm power to electric
power, what would it be able to power?
 What was the range of powers for the leg
exercises?
 If you could transfer this leg power to electric
power, what would it be able to power?
 Is the power output of your arm muscles more or
less than you thought it would be? (Hypothesis)
 Is the power output of your leg muscles more or
less than you thought it would be? (Hypothesis)
 What is the relationship between work and power?
 What is the relationship between mass and
weight?
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cell phone charger (2 W)
clock radio (7 W)
light-bulb (15 W)
laptop computer (50 W)
game system (100 W)
TV (300 W)
refrigerator (600 W)
microwave oven (900 W)
AC Unit (1500 W)
electric stove/oven (3000 W)
electric clothes dryer (5000 W)
Make-up Data
Exercises (5 Reps for each
exercise)
• Arm curls
• Push ups
• Jumping jacks
• Knee bends
Distances
• 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 s
Find 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
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Title (2)
Objective (3)
Pre-Lab (5)
Hypothesis (5)
Materials (2)
Data (5)
Conversions (5)
T-Charts (12)
Conclusion (16)
Order (5)
Total = 60