Powerhouse Lab
In this lab you will explore the difference between work and power. Work is the amount energy transferred into or out of a system. Work is measured in Joules, J
When you walk up stairs you are lifting your weight a certain height. This is called doing work against gravity. When you do work against gravity you are transferring potential energy to the object. This potential energy is coming from the chemical energy that is released in your muscles as they metabolize food. You could day that you are converting stored chemical energy into stored gravitational potential energy.
work against gravity = weight x height
( where weight is in Newtons and height is in meters)
The rate at which you convert one form of energy into another is called power. Power is measured in Watts, W. A 100 W light bulb converts 100 Joules of electrical energy into light energy every second. If you “use” 3000 W of energy you have converted 3000 J of one type of energy onto some other form every second. The faster you convert the energy the higher the power “used”.
power = work ÷ time
Prodcedure
1. You will do the following activities:
• lift a mass with your arm straight up one meter.
• walk up a flight of stairs that is at least one meter high.
2. Determine the weight of your object in Newtons. You will need to estimate the number of pounds the object weighs. Then convert pounds to Newtons using the fact that 1 lb = 4.4 N. So if you weigh 200 lbs your weight would be 200 ( 4.4) = 880 N. Put this in the chart for both trials.
3. Now determine how high the object will be lifted off the ground. This will be the actual height of the stairs when you are doing that activity.
4. Now perform each activity very slowly and time yourself. Record the times in the data chart.
5. Now perform each activity very quickly and time yourself. Record the times in the data chart.
6. You will need to attach two pictures showing you doing each part of the lab.
Data Chart: Type your values in this chart.
activty Weight (N) Height (m) Work = weight x height (Joules) Power = Work ÷ time
( Watts)
Stairs Slow
Stairs Fast
Lift Object Slow
Lift Object Fast
Conclusions: Type your answers in COMPLETE sentences below each questions. Use az different color or highlight the answers.
1. Do you do more work against gravity while you were running or walking? Explain.
2. Do you do more work lifting an object fast or slow? Explain.
3. Do you “use” more power when you run up stairs or down stairs? Explain.
4. Do you “use” more power when you lift something quickly or slowly? Explain.
5. A friend says to you, “ I am so tired !! I did so much work running up the stairs.” Use what you have learned about work and power to explain why or why not his statement is correct.
Attach a picture of you doing each activity below:
Save your work and submit in the Lab Blog Assignment.