Estimations and Models Exercises

1 Unit Conversion

There are 1055 joules in a BTU. If you have 20 BTU of energy, what is that quantity of energy when expressed in kilojoules?

2 Energy Density

There are 115,000 BTU in a gallon of gasoline. How many gigajoules are in a 12-gallon tank of gas?

3 Mega to Giga

Express the quantity of 10,000 megajoules in gigajoules using our factor-label unit conversion method.

4 Prefixes

How many kilojoules are in a megajoule?

5 Power to Energy

You have a hair dryer that uses approximately 750 watts of power. If you use this hair dryer for 6 hours, how much energy does it use in kilowatt-hours?

6 Energy to Power

A phone battery can store approximately 22 kJ of electrical energy. What power in watts will charge the battery in 4 hours.

7 Power Plant Energy

A power plant produces 1.5 MW of power while running. If this plant runs continuously for one day, how much energy in joules (or gigajoules) does it produce?

8 World Power

The world uses approximately 500 exajoules per year. Express this as a power in watts.

9 Custom Energy Quantity

Come up with your own interesting energy quantity. It could be of any energy type. This exercise is to get you thinking about how to estimate the quantity, we are not interested in an accurate estimation yet.

  • Define your energy unit clearly with a physical description.
  • Define the input quantities clearly.
  • Optional: Express the quantity in units of joules.

10 MacKay Balance Sheet Reading

Please read this chapter from MacKay Sustainability Without All of the Hot Air.
You can also find a link here. Then answer the following questions in complete sentences:

  • Can energy be created or destroyed?
  • How would you explain energy to a non-expert?
  • How would you explain power?

11 Personal Gasoline Model Outline

In your notes or on a piece of paper, write the components simple energy model (on a single page) to predict your annual automobile gasoline consumption. If you are comfortable, try to make an estimate. If not, clearly articulate what you know and don’t about making an estimate. Take a photo of this model and submit it as your assignment.

12 Personal Gasoline Model Estimate

Revisit your personal gasoline model from the last class period. Now, using your knowledge of energy quantities and units, make a quantitative estimate of your gasoline use in a year.

Write this out on paper with enough clarity that someone could understand your model. Then take a photo and upload to Canvas.

13 GEP 280 and ER 100 Readings

Please read the following two links and answer these questions in complete sentences.

14 H&K Chapter 2 Energy Mechanics

As you go through the reading, focus on the concepts. You will not be expected to reproduce all the calculations in this chapter. You also don’t need to read the appendix on Newton’s Laws of Motion.

Here is a link to the reading

  • Give an example of a simple energy conversion you find interesting and explain what type of input energy is converted into what type of output energy
  • Give an example of an energy conversion that has more than one step and explain each of the energy steps.