Measuring Power

We’re going to practice measuring and calculating real life stuff (because science isn’t just in a textbook, is it?) When I taught engineering classes, most students had never analyzed real bridges or tools before – they only worked from the textbook. So let’s jump out of the words and into action, shall we? This experiment is for Advanced Students.

Before we start, make sure you’ve worked your way through this experiment first!

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For this experiment, you need:

1. Meter or yard stick
2. A stopwatch or timer
3. Object

Here’s what you do:

Download Student Worksheet & Exercises

1. Grab your 100 gram object, put it on a table.

2. Now lift it off the table straight up until you lift it one meter (one yard).

3. Start the timer and at the same time start lifting the object up and down 20 times.

4. Stop the timer when you’re done with the 20 lifts.

So, do you have the power of the Dodge Viper? Hmmm, probably not but let’s take a look.

First of all figure out how much work you did. Work = force x distance so take the force you used and multiply that by the distance you moved it. In this case, you can multiply 1 Newton x 20 meters and get 20 Joules of work.

Now figure out how much power you used. Power is work divided by time so take your work (20 Joules) and divide it by how much time it took you to do that work.

For example, if you lifted the block 20 times (doing 20 Joules of work) in 5 seconds, you did 20 Joules/5 seconds = 4 Watts of power. To convert Watts to horsepower we multiply by .001 so in this example, you did 4 x .001 = .004 horsepower. Not exactly vroom vroom!

Exercises

1. What is work?
   1. Force divided by distance
   2. Force times distance
   3. Energy required for power
   4. Kinetic and potential energy
2. What is power?
   1. Work divided by time
   2. Work multiplied by time
   3. Energy used in an exercise
   4. Calories over time
3. How do we measure work? Name one unit.
4. How do we measure power? Name one unit.

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