Work and Power - Fayetteville State University



Work and Power

Purpose: In this experiment you will become familiar with work and power through means of walking and running.

Materials: Calculator, Timer, Meter Stick

Introduction:

The word WORK represents a concept that has a special meaning in science that is somewhat different from our everyday usage. WORK is defined as the product of the applied FORCE and the DISTANCE through which the force acts (W=FD). You are doing work when you walk up the stairway since you are doing work when you are lifting yourself through a distance against the force of gravity.

Procedure:

1. Work in groups. Individual members have to complete the task.

2. The vertical height of the stairs can be found by measuring the height of one step and multiplying it by the # of steps.

3. Measure and record the time taken by each member to walk normally up by the flight of stairs. Record the distance in feet.

4. Measure and record the time taken for each person to run up the stairs as fast as can be accomplished SAFELY.

5. Calculate the work accomplished, power level developed and horsepower of each person while walking and while running up the flight of stairs.

Name __________________

__________________

__________________

Date___________________

Work and Power Report Sheet

Calculate the work you do in a) walking and running up a flight of stairs and b) running up a flight of stairs from your data. The following sequence of steps will help you get to the answer. SHOW ALL CALCULATIONS AND UNITS!

a. Your weight = _______________ 1b = __________________ Kg

b. Acceleration due to gravity = ___________________

c. Height of a single step = _____________________ cm

d. Height of the 11 steps = _______________________ cm = ____________________ m

WORK = _______________________ N.m = ______________________ Joules

The rate at which energy is transformed or the rate at which work is done is called POWER (P) and is defined as work per unit time, P = W/t. The unit is a Joule per second and is also called Watt (Though originally power was defined in HORSE POWER and units like ft. lb/sec).

e. The time it takes you to walk up the stairs = ________________ sec

POWER = ______________ Joules/sec = ____________________ watts

=_______________________ horse power = ft. lb/s

f. The time it takes you to run up the stairs = ______________ sec

POWER = ________________ Joules/sec = ___________________ watts

= _______________________ horse power = ___________ ft.lb/s

Questions: Answer the following questions after completing the exercise on the next page.

1. Explain why there is a difference in the horsepower developed in walking and running up the flight of stairs.

2. How much "effort" is required to move a 300 kg object up a smooth board 5.00m long if one end of the board is placed in a windowsill 1.50m above ground?

3. Could the horsepower developed by a slower moving student ever be greater than the hp

developed by a faster moving student ?

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