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11th Grade Physics Lab: Can You Feel the Power?Course Instructions: Follow the instructions on the lab sheet. Complete all parts of the lab and write your answers and results on the lab sheet.See attached lab and rubric.
lab_6c__can_you_feel_the_power.pdf

lab_6c__rubric.pdf

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Name ____________________ Class ______________ Date ______________
TEKS 6C Calculate the mechanical energy of, power generated within, impulse applied to, and
momentum of a physical system. TEKS 2E Design and implement investigative procedures, including
making observations, asking well-defined questions, formulating testable hypotheses, identifying
variables, selecting appropriate equipment and technology, and evaluating numerical answers for
reasonableness. TEKS 2F Demonstrate the use of course apparatus, equipment, techniques, and
procedures, including multimeters (current, voltage, resistance), triple beam balances, batteries,
clamps, dynamics demonstration equipment, collision apparatus, data acquisition probes, discharge
tubes with power supply (H, He, Ne, Ar), hand-held visual spectroscopes, hot plates, slotted and hooked
lab masses, bar magnets, horseshoe magnets, plane mirrors, convex lenses, pendulum support, power
supply, ring clamps, ring stands, stopwatches, trajectory apparatus, tuning forks, carbon paper, graph
paper, magnetic compasses, polarized film, prisms, protractors, resistors, friction blocks, mini lamps
(bulbs) and sockets, electrostatic kits, 90-degree rod clamps, metric rulers, spring scales, knife blade
switches, Celsius thermometers, meter sticks, scientific calculators, graphing technology, computers,
cathode ray tubes with horseshoe magnets, ballistic carts or equivalent, resonance tubes, spools of
nylon thread or string, containers of iron filings, rolls of white craft paper, copper wire, Periodic Table,
electromagnetic spectrum charts, slinky springs, wave motion ropes, and laser pointers. (Also TEKS 2I)
Lab 6C: Can You Feel the Power?
Directed Inquiry
Introduction
Power is the rate at which energy is transferred. Because energy is the ability to do work, power is also
the rate at which work is done. One reason that we use machines is that many of them can do work at a
faster rate than the human body alone. In other words, machines have greater power. Both work and
energy are measured in joules, J. So power, the rate of work, is measured in joules per second, J/s. When
you lift an object, you do work on it. The work you do is equal to the weight of the object in newtons
multiplied by the vertical distance in meters that you move it: work = weight × distance. When you
calculate work this way, the result is in newton•meters, which is the same as joules.
You make observations in every investigation. Sometimes you also make measurements. Both
measurements and observations are data. You can interpret this data to learn about the questions that you
tested in the investigation. In this lab, you will interpret data to compare the power used by several bodies
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in a “stepping” exercise. When different people with different weights do the exercise at different speeds,
how does the power output vary?
With these statements in mind, preview the Lab Investigation. Then answer the questions in the spaces
provided.
1. What are the three measurements you need to make in order to calculate power? What are the
units of those measurements?
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2. Suppose Students A and B do the stepping exercise in equal amounts of time and at the same rate
of speed. If Student A is heavier than Student B, which student exerts more power? Explain.
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Materials

Scientific calculator
Meter stick
stopwatch or clock with a second hand
board, about 4 cm × 25 cm × 120 cm
18–20 books, each about 2 cm thick
Procedure
1. Construct a step by making two identical stacks of books. Each stack should be about 20 cm high.
Place a board securely on top of the stacks of books so that the ends of the board are even with
the outside edges of the books.
CAUTION: Be sure to have your partners hold the board steady and level throughout the
activity.
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2. Measure the vertical distance in centimeters from the floor to the top of the board. Convert to
meters by dividing by 100, and record this height in the data table.
3. Step up onto the board with both feet and then step backwards off the board onto the floor. This
up-and-down motion is one repetition. Make sure you are comfortable with the motion.
4. Calculate Calculate the work you do in stepping up onto the board just once. Then calculate the
work you would do by stepping up onto the board 20 times. Record both answers in your data
table.
your weight (N) × height of board (m) = gravitational potential energy
= work done in stepping up onto board
5. Have one partner time how long it takes you to do 20 repetitions performed at a constant pace.
Count out loud to help the timer keep track of the number of repetitions. Record the time in the
Trial 1 row of your data table.
6. Calculate Calculate the work you did for 20 repetitions. Then calculate your power for the 20
repetitions. Record your data for Trial 1.
power = energy transferred/time = work/time
7. Repeat steps 5 and 6, but climb the step more slowly than you did the first time. Record the new
data for Trial 2.
8. Switch roles with your partner and repeat Steps 3 through 6, using the weight of that partner.
Record your data for Trial 3.
9. Repeat Step 7 using your partner’s weight—the same weight used in Step 8. Record the new data
for Trial 4.
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Analyze and Conclude
1. Interpret Data Compare the amount of power you produced during your first and second trials.
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2. Calculate What is the gravitational potential energy gained from stepping up onto the board?
How does this amount of energy compare to the amount of work required to step up onto the
board?
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3. Observe Describe the amount of work you did during your first and second trials.
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4. Draw Conclusions Did you and the other student performing the stepping do the same amount
of work? Did you both produce the same amount of power? Explain your answers.
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5. Predict Would you do more work walking up a flight of steps or running up the same steps?
Would you exert more power when running? Explain.
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Directed Inquiry Post-Lab
1. Draw Conclusions Describe two ways that a single person doing the step exercise can change
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2. Design an Investigation Describe an investigation to determine which of two people of
different weights could exert the greater power using the step apparatus.
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3. Summarize Describe what you learned about the power exerted when a person does the step
exercises. List any questions you still have.
What I learned: _______________________________________________________________
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What I still want to know: ______________________________________________________
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Name ____________________ Class ______________ Date ______________
Open Inquiry
Problem
Can you change how much power you use while exercising?
Materials

calculator
meter stick
stopwatch or clock
footstool
1. Imagine that you are talking with a friend about the amount of physical strength it takes to leap up
onto a table. The friend thinks that someone who is light in weight does more work than a heavier
person who can leap up just as high. Your friend’s reasoning is that the smaller person probably
has less muscle mass, and therefore a leap of equal height means more work is being done. You,
on the other hand, have just learned the scientific definition of work. So you know that the lighter
person is actually doing less work than the heavier person. To prove your point, design a simple
investigation to demonstrate how much work is done during a given physical movement and then
calculate how much power is required to repeat that movement over a given period of time.
2. You will need to use the formulas below in your investigation.
a. work (in Joules, or newton•meters) = weight (force in newtons) × height (in meters)
b. (weight) lbs ×
1 kg
× 102m = weight in newtons
2.2 lb
s
c. power = work/time
3. With your partners, think about a physical movement or exercise you want to use in your
investigation. Your teacher will provide you with something you can step or hop onto. Your
movement must involve moving vertically in a way that is easy to repeat and easy to measure.
Each of you should take turns trying this movement and figuring out a pace that will allow you to
repeat the movement over the course of 20 or 20 seconds without risking injury or tiring yourself.
Your pace can vary, but aim for a steady rate of movement for yourself.
4. Set up an investigation in which each of you, one at a time, repeats the movement at a regular
pace over a given period of time. You will measure work and gather other data that will help you
calculate power. Do at least one other trial where you perform the movement (work) at a slower
pace. Below, describe your procedure and record the data. As you design your procedure,
consider these questions:
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a. To measure how much work goes into moving a person’s body vertically, what data
do you need?
b. What are the units for those data? Will you need to do any conversions?
c. Power is a measure of the rate at which work is performed. To measure rate, what
two things will you need to measure during each trial?
d. How can you change the amount of power that is used without changing the time
period or the work per movement?
5. Have your teacher review your procedure and data table. Once approved, carry out your
procedure and record your results below.
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Analyze and Conclude
1. Calculate When you calculated work, what factor varied from one person to the next, and how
did this factor affect the values you calculated?
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2. Interpret Data Explain how power changed when you reduced the rate of movement.
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3. Observe Did work change when you reduced the rate of movement? Explain.
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4. Infer What units did you use for power? Why?
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5. Design an Investigation In terms of work, energy, and physiology, this investigation failed to
account for every bit of muscular effort that your body had to make to complete each repetition.
Why? How could you revise your investigation to correct this?
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Name ____________________ Class ______________ Date ______________
Open Inquiry Post-Lab
1. Draw Conclusions Imagine identical twins who are the same height and do the same physical
activities, yet one is heavier than the other. They go on a diet together. They eat the same foods
and do the same exercises each day, but the heavier one loses weight at a much faster rate than
the other. Use your knowledge of work and power to explain this.
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2. Apply How could you measure the amount of work done by an elevator as it moves from the
first floor to the fifth floor and picks up one new passenger at each floor on the way up?
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3. Summarize Describe what you learned about the power exerted when a person does the step
exercises. List any questions you still have.
What I learned: _______________________________________________________________
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What I still want to know: _______________________________________________________
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Physics Hands-on Lab Rubric
Top Scores (16–20) – The top scoring students will do the following:
• Present ideas for a laboratory experiment that would accurately measure principles studied in this laboratory
• Develop reasonable hypothesis regarding the variables measured in this laboratory
• Accurately record data in well-organized and appropriately labeled data tables, as appropriate
• Graph data in appropriate graphs using all the proper conventions and labeling procedures
• Analyze data to show a deep understanding of physical principles
• Draw conclusions based on experiments that show how physical concepts affect the world around them
Middle Scores (10–15) – Acceptable scores for students go to those who do the following:
• Present ideas for laboratory experiment that would measure principles studied in this laboratory, although the
experiment may not actually work or measurements may be inaccurate
• Develop hypothesis about variables measured in this laboratory, although hypothesis may be unreasonable
• Record data in organized tables, as appropriate
• Graph data in graphs, but may have some errors in labeling or organization
• Analyze data with a basic understanding of physical principles
• Draw conclusions based on experiments using direction from questions posed in lab
Low Scores (0–9) – Students score poorly when they:
• Do not present ideas for laboratory experiment that would measure principles studied in this lab or these ideas
• Do not present hypothesis about values measured in this experiment
• Record data in tables in a disorganized manner
• Create graphs that do not correctly reflect the data and are difficult to interpret
• Incorrectly relate experiments to physical concepts