1. Define force, energy and power; units of measure
- Force- whatever can cause an object with mass to accelerate. Measured in Newtons.
- Energy- a scalar physical quantity that is a property of objects and systems which is conserved by nature. The ability to do work. Measured in Joules.
- Power- the rate at which energy is transformed from one form to another or transferred from one object to another. Measured in watts or joules.
2. Why is Co2 a greenhouse gas and nitrogen not?
CO2 absorbs and traps heat in the earth’s atmosphere and nitrogen does not.
3. My question (number 3)
Solar Energy is incident at the top of the Earth’s atmosphere at the rate of about 1368 watts per square meter. This energy effectively falls on the cross sectional area of the planet. Calculate the total rate at which solar energy arrives at Earth.
Find cross sectional area of the planet. A=(3.14)r^2
R= 6.37 x 10^6 m
A= 1.274760 x 10^14 m
Multiply cross sectional area times rate
(1368 W/m2)(1.274760 x 10^14)= 1.743 x 10^17
How does this compare with energy flux at the earth’s surface?
31% of sunlight gets reflected back into the atmosphere.
69% of sunlight actually reaches the earth’s surface.
45% is converted right into solar energy
23% is evaporated
1% goes into the energy of winds and currents
0.o8% is used for photosynthesis.
Therefore if you multiply the number above by .69 you get the actual amount of solar energy that hits the earth’s surface. (1.202 x 10^17) This number is considerably smaller than the actual amount of solar energy that hits the top of the atmosphere.
What factors affect this quantity?
Most of the solar energy is reflected back into the atmosphere via clouds and reflective particles in the atmosphere, but ice, snow, deserts and other surface features can have the same effect.
I really enjoyed what we did this week in class. Because everyone is an honors student the issues are given life by the presenters and their opinions. I think the lesson could only have been made better if we had been given a little background information before hand; I haven’t take physics since the 11th grade and I don’t really remember how all the formulas work as simple as they may be. Maybe a review sheet would help.
1 comment:
Good detail on the question no. 3.
And, feedback on how the class is going.
Today's lecture was intended to give some of the background you mentioned. Sometimes it's better to talk about things after students have a little time to understand the issues and what they need to know. That can also be frustrating process. I'll keep trying different ways, so it helps to know when things work.
You gave good basic info in #1. Could expand the discussion a little, maybe with examples.
#2 needs more discussion of why.
Post a Comment