Fall 2006†††††††††††††††††††††††††††††††††††††††††††††††††† Name______________

††††††††††††††††††††††††††† Measure your Horsepower

 

This page is your pre-lab.All of this page is to be completed before you arrive in class.This material is covered on pages 64-66 in your text.

 

Define Work:

 

 

What is the relationship between the force and the direction of the motion in the above definition?

 

 

What are the units of work? _______________________

 

Write the definition of a joule in terms of newtons and meters.

 

 

Define power:

 

What are the units in which power is measured? ___________________

Write the definition of a watt in terms of joules and seconds.

 

 

Calculate the work done if an 85 kg person climbs vertically 6 meters.Clearly show each step in the solution.

 

 

 

 

 

How does this work change if the climbing is done at a 45-degree angle, but the total vertical movement remains 5 meters?Explain your answer!

 

 

 

 

If it takes the person 10 seconds to climb the 6 m in the previous problem, what is the person's power?Show your work clearly.

 

 

 

 

How many horsepower is this? (Note: 1 horsepower is 746 watts)

Clearly show your work!

 

 

 

What is your weight in pounds? _________________________

Note: There are 2.21 lbs/kg

 

 

Convert the above to give your mass in kilograms_____________________

ALL OF THIS FIRST PAGE IS TO BE COMPLETED BEFORE COMING TO LAB!

In Lab

Calculate the amount of work you would do if you climbed stairs that were 10 meters high.Clearly show how you arrive at your answer!

Have the instructor check your answer before proceeding.†† ______

 

 

 

 


If the weather is good, do the following outside on the football stadium, otherwise use the stairs from the basement of the Science Center to the top floor (climb all 4 flights of stairs from the basement to the third floor).Your instructor will tell you which to do.

 

Determine the average height of one step.To do this measure every 4 steps, write the results on the side of this page, then average your results to obtain the average height of a step:________ (in meters)

How many steps are there? ______________

 

Calculate the total vertical rise of all the steps (number of steps________ times the height of one step_________: = ___________ m

 

Measure the amount of time necessary for you to climb the stairs.You have the choice of doing this at your maximum speed to calculate your maximum horsepower, or you may move up them at your normal pace and calculate your normal power output.Repeat this two times and use the average in your calculations.

 

Time 1 = _________†† Time 2 = _________Average time = __________

 

Calculate the work done: Clearly show each step in the calculation.If you need assistance, speak with the instructor.

 

Work done by climbing the stairs =

 

 

 

Calculate the power:

 

Power =

 

Convert your answer to horsepower: (See front page!)

 

Horsepower =

 

Have the instructor check your work. _______

The instructor will indicate a number of books to you that are to be placed in 3 equal stacks beside one of the lab tables.He will indicate to you the mass of the books.†† Mass of books = _____________

 

 

Vertical distance books are moved? (Height of table.) h = ____________

 

 

 

Now have someone time you as you lift the books onto the table.

time = _____________

 

Calculate the total work done. Clearly show your work!

Work done in lifting the books onto the table =

Data†† †††† Formula††††††† Work

 

 

 


Calculate the power: Clearly show your work!

Data†† †††† Formula††††††† Work

 

 

 

 

Convert to horsepower:

 

 

 

If you maintained this output for one hour, how many kilowatt-hours of work would you have done? ____________________________

 

Have the instructor verify your answers above _____

 

In Marshall, the cost of energy is less than 8 cents per kilowatt-hour.If you worked for the same wage at the same pace ($0.08/kwh), calculate what your hourly wage would be.Clearly show your work. Write your answer below:

Amount I would receive for an hourís work =

 

Calculate what your pay for a 40-hour week would be. Write your answer below:

(1)Amount I would be paid for 40 hours work =

 

Have the instructor verify your answer _____

 

If you worked at this pace for 40 hours, how many kg of books could you put on the table? Hint: Calculate how many books you would put on the table in one minute, and then multiply by the number of minutes in 40 hours.

 

 

___________________

 

(2)How much would electricity cost to run a conveyor belt that did the same amount of work?††††††††††††††††††††††††††††† ____________________

(Note that you have already done this calculation in point (1) above!)

 

If you hired a person to do this work and paid them $8.00 per hour for the 40 hours, what would they receive for this hard work? _________

 

Yet if you had an electric motor to do the same amount of work the cost would be your answer to (2) above.How much more do you pay the person than it would cost to use an electric motor to do the work?Express your answer as a whole number, 4 times as much, etc.