Assignment 5 - Answer Key

This Assignment covers material that it is covered in Canvas Sections 3.2 - 3.5. It will be due after we complete Section 3.5.  You  should work on questions 3 through 8, however,  immediately after finishing Canvas Section 3.2 while this information is still fresh in your mind.  Questions 1, 2, 9 and 10 are covered in Sections 3.3 -3.5.

 

1.  Which of the 3 modes of energy transfer (conduction, convection or radiation) is the BEST choice for each of the following

a.   Billowing Clouds: Convection. Whenever energy is being transferred in a gas or a liquid, convection is the most efficient method of transfer.

b.  Frying eggs in a pan: Conduction. This is the best choice. The pan is made of metal which is a good conductor transferring heat through molecular motion to the eggs.

c.  Sand at the beach too hot to walk on: Conduction or Radiation. A case for either could be made and both are correct.

2.  Which has a higher albedo; rough water or smooth water? Rough Water.  Smooth water is dependent on the angle of the sun. Water only has a high albedo when the sun is near the horizon (around sunrise or sunset). But rough water has a higher albedo throughout the day because it has many different angles to reflect sunlight regardless of sun angle.

3.  How many times during the year are noon sun's rays at a 90° angle for a location at 16°N? Two times  (either May 5th or August 10th). The sun is directly overhead at 16°N once between March and June as the sun's declination shifts north (May 5th) and a second time as the sun's declination moves south between June and September (August 10th). Look at an analemma and should be clear.

Please give me the date (or dates) on which this occurs . May 5th or August 10th

Read the analemma at 16°N and note the two dates the line intersects this latitude..

 

4.  What is the angle of the noon sun with respect to the horizon at a latitude of 38.5°N on June 22?

Latitude 38.5°N

Date: June22

Declination of the Sun on June 22:  23.5°N.        (this is the summer solstice - you should know the declination of the sun on the solstices and the equinoxes without the use of an analemma)

The declination and the latitude are in the same hemisphere (both north) so you subtract

38.5 - 23.5 = 15.              90 - 15 = 75° is the angle of the sun above the horizon at solar noon on this date at this latitude

 

5.  What is the angle of the noon sun with respect to the horizon at 85°S on December 22?

Latitude: 85°S

Date: December 22

Declination: 23.5°S     (this is the winter solstice - you should know the declination of the sun on the solstices and the equinoxes without the use of an analemma)

The latitude and the sun's declination are in the same hemisphere so you subtract.

85 - 23.5 = 61.5.               90 - 61.5 = 28.5 ° is the angle of the sun above the horizon at solar noon on this date at latitude

 

6.  What is the angle of the noon sun with respect to the horizon at 80°S on June 22?

Latitude: 80°S

Date: June 22

Declination: 23.5°N (summer solstice)

The latitude and the sun's declination are in opposite hemispheres so you add.

80 + 23.5 = 103. 5.        90 - 103.5 = -13.5°

How is a negative number possible? At the N. Hemisphere summer solstice at 80°S the sun will never rise. Where is it? Below the horizon. A negative number indicates that the sun is below the horizon.

 

7. What is the angle of the noon sun with respect to the horizon at 73°N on November 10?

Latitude: 73°N

Date: November 10th (this is not a solstice or equinox so you have to look up the declination using the analemma)

Declination: 17°S

The latitude and the declination are in opposite hemispheres so you add.

73 + 17 = 90.              90 - 90 = 0°  (stop and think about it....you are above the Arctic Circle a month out from the Winter Solstice. So far north, on this date the Sun doesn't above the horizon...instead at its highest its right on the horizon)

 

8. What is the angle of the noon sun with respect to the horizon at 7°N  on September 5?

Latitude: 7°N

Date: September 5 (gotta use the analemma for this one - not a solstice or a equinox)

Declination: 7°N

The latitude and the declination are in the same hemisphere so you subtract.

7 - 7 = 0.            90 - 0 = 90° ( you are almost at the Equator and its only a few weeks from the Equinox. Makes sense that the angle of the sun at solar noon would be 90° at 7°N on Sept. 5th)

 

9.  Convert 150°C to Fahrenheit.

The formula for converting Celsius to Fahrenheit

T_(°F) = 150°C × 9/5 + 32 = 302°F

10. Convert -40°F to Celsius.

The formula for converting Fahrenheit to Celsius

T_(°C) = (-40°F - 32) × 5/9 = -40 °C