WORK AND POWER INTRODUCTION Work is a measure of the energy transferred from one object to another by the application of a force through a non-zero distance. Power is the rate of doing work or the rate at which energy is transferred from one object to another.

In this experiment, each student will perform a simple task consisting of climbing one flight of stairs. The force required to move the student from one level of the building to another is equal to the average normal force between the student's feet and the stairs. That force is, in turn, equal to the weight of the student. The amount of work performed by the student is, therefore, the weight of the student times the distance climbed. The amount of energy expended in lifting the student one flight of stairs is equal to the work performed in accomplishing the task.

The average power developed by the student is related to the work performed but is also a function of the time it takes the student to mount the one flight of stairs. Even though the same amount of work is performed each time the student climbs the stairs, the power developed by the student will be different if the time taken to complete the climb varies.

In this experiment each student will climb one flight of stairs two times, intentionally varying the amount of time required to move from one floor to the next.

MATERIALS 1 meter stick - in kit 1 stopwatch or cellular phone with timing capabilities to at least the tenth of a second 1 scale (or estimate personal weight) 1 flight of stairs (make sure that no other person is placed at risk of an accidental collision with you, the climber)

PROCEDURE Measure the distance, in meters, from the floor to the top of the first step. Multiply the height of one step by the number of steps in the stairway to get the vertical distance being climbed. Calculate your weight (in newtons).

Time yourself as you climb the single flight of stairs at a rather slow, comfortable pace. The stopwatch should be started when you begin the ascent and should be stopped when both of your feet reach the upper floor. Record the time in seconds.

Repeat step three but this time climb as rapidly as possible without causing discomfort. Follow the same procedure for measuring the time.

Calculate and record the work performed by you by applying the equation Work(W) = Force (F) x distance (d) where the force is equal to the weight of the climber and the distance is the vertical height lifted. If the force is in newtons (N) and the distance in meters, the calculated work will have the units of joules (J).

Calculate and record the power developed by you both walking and running up the stairs from the equation Power (P) = Work (W) time(t). If the work is in joules and the time is measured in seconds, the power will have the units of watts (W).

Convert the power developed in each situation from watts to horse power (hp) using the equality 1 hp = 746 W.

DATA (Question #1)

	WALKING	RUNNING
Force Applied (weight) (N)
Vertical height lifted (m)
Time required to walk up the stairs (s)		X
Time required to run up the stairs (s)	X
Work Performed (J)
Power (W)
Horsepower developed

QUESTIONS 1.)Explain why the work performed remained the same whether you ran or walked up the stairs.

2.)Explain why the amount of power developed was different when walking up the stairs and when running up the stairs.

3.)Describe the conditions that would lead to you developing more power than someone else even though you climbed the same number of stairs more slowly that the other person.

4.)Suppose you walked the same distance you climbed up the stairs but stayed on a single floor without climbing any stairs. Would you perform the same amount of work or develop the same power you did climbing the stairs? Explain your answer.

5.)Describe an experiment to measure power developed over a period of time longer than the short burst developed climbing a flight of stairs.