Your Stair-Climbing Power

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					                              Your Stair-Climbing Power

     Safety First! Be very careful when climbing stairs. Do not run up the stairs, but
     walk at a rapid rate, and hold onto the handrails. If you become tired, out of breath, or
     experience any other symptoms of discomfort, do not continue with the procedure. If
     you are unable to climb stairs for health reasons, tell your teacher and participate by
     timing another student who is able to do so.



Introduction:

Work equals force times the distance through which the force acts. Force is expressed in
newtons (N) and distance is expressed in meters (m). Work is expressed in newton-
meters, or joules (J). The rate at which work is done is called power. Power equals work
÷ time. If work is in joules (J) and time is in seconds (s), power is expressed in
joules/second (J/s). One J/s is the same as 1 watt (1 W), a unit named after British
scientist James Watt, inventor of the steam engine.

Problem:

How much work do you use when climbing stairs?

Materials:

Bathroom scale                  metric ruler
flight of stairs                stopwatch

Procedure:

 1. Work with a partner. Use the bathroom scale and weigh yourself. (To convert
    from pounds to Newtons multiply by 4.45, to convert from kilograms to Newtons,
    multiply by 9.8)

 2. Measure the height of one step of the stairs that you are going to use. Convert the
    length to meters and record your results.

 3. Count the number of steps that you will be climbing. (Multiply this by the height
    of one step to find the total height.)

 4. Climb the stairs as quickly as you can and find the average of your three times.

 5. Change roles with your partner so that they can get their results.
Observations:


                      Weight in Newtons (N)


                      Height of one step (m)


                      Number of steps


                      Total height of stairs (m)


                      Time for First Climb (s)


                      Time for Second Climb (s)


                      Time for Third Climb (s)


                      Average Time of Climbs (s)


Analysis:

   1. Were the three climbs roughly the same, or did they vary considerably?

   2. Did you feel as if you exerted the same effort on each climb? Explain.

   3. Calculate your work in climbing the stairs. To do so, multiply the total height of
      the stairs by your weight in newtons (which is the downward gravitational force
      you overcame with an equal upward force when you climbed). Express your
      answer in joules.

   4. Calculate your power output for the climb. To do so, divide the work by your
      time. Express your answer in watts.

   5. If you had climbed more slowly, how would your work have been affected? How
      would your power have been affected? Explain your answers.
6. Compare your power with other students. Did all of the students who climbed the
   stairs in the same amount f time have the same power output? Explain your
   answer.

7. How does your power output in climbing the stairs compare to the power output
   of a 100-watt light bulb? If your power could have been harnessed and the energy
   converted to electricity, how many 100-watts bulbs could you have kept burning
   during your climb?

				
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posted:11/19/2011
language:English
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