Quiz Answers
Jun. 17th, 2008 09:26 am![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
asterrocIn case anyone's interested, I thought I'd post some answers to the quiz questions I posted the other day asking people for help in timing online quizzes.
Regarding the timing issue, everyone reported that it took them a very short time to type their answers - admittedly it's a self-selected group (I doubt slow typers would enjoy blogging all that much, and people who hate science probably wouldn't be answering these questions for me), but still it gives me a starting point. My plan with my class is to (a) ask students during the first week about their typing skills, (b) unless any of their answers worry me, I'll give the same amount of time for the first quiz as I would give in a face-to-face class, (c) I'll look at the statistics of how long it took them to complete the quiz and adjust subsequent quizzes accordingly.
So for the answers, below are what I was looking for, key words/concepts bolded, along with some items that would likely lose the person points and why.
1) Explain the cause of the seasons.
As the Earth orbits the Sun, its axis is tilted by 23.5ยบ. This results in sunlight hitting the surface of the Earth more or less directly (resulting in more or less intense sunlight) depending upon which part of the Earth is pointed towards the Sun at that particular time of year. The tilt also results in the length of the day changing through out the year.
Distance from the Sun would lose you points: the Earth's orbit is so close to circular that the distance does not make any measurable difference in the weather on Earth. Earth is actually closest to the Sun on Jan 3 or so, Northern Hemisphere Winter, Southern Hemisphere Summer - if it were simply distance from the orbit then both hemispheres would have the same season. Saying the tilt makes one part closer to or farther from the Sun is a little more creative (and would gain partial credit from the tilt), but also doesn't make a big enough difference.
2) Is Pluto currently considered a planet by astronomers? Why or why not?
The current definition of planet require an object to orbit the Sun, be small enough to not be undergoing nuclear fusion, be large enough to be round from self-gravitation, and have cleared its orbit. Pluto fails the last criterion, as there are many other objects orbiting just outside Neptune's orbit, variously called plutinos, plutiods, trans-Neptunian objects, and a larger group called Kuiper Belt Objects.
3) Compare and contrast the Greenhouse Effect and the Ozone Layer.
The greenhouse effect is caused by greenhouse gases (such as CO2, H20, CH4, etc.) distributed throughout the atmosphere (or closer to the ground) while the ozone layer is one region of the stratosphere containing O3. The ozone layer acts simply to absorb much of the incoming UV and prevent it from reaching the ground. The greenhouse effect is more complex, as (nearly) full spectrum light hits the ground, some is reradiated as IR, and then the greenhouse gases trap much of the IR light within the atmosphere.
FWIW I know the wording of this question needs improvement. A better wording might perhaps be "Greenhouse Gases and the Greenhouse Effect, and the Ozone Layer and its effects." I typically explain what I'm looking for before giving this quiz question - I usually tell the students this will be the next quiz, and explain that the two are "opposite and complementary." The main thing I'm looking for here is for the students to distinguish that they are two entirely separate phenomena, since the media always conflates them.
4) Why do astronauts in the Space Shuttle experience weightlessness?
As the Space Shuttle orbits the Earth it is moving just fast enough that as the Shuttle (and everything within) falls towards the Earth due to gravity, the surface of the Earth (and the path of their orbit) curves away underneath them by the same amount that they fall due to the gravity. Therefore they are in free fall, or experience weightlessness even though they are still influenced by gravity. (Compare this situation to Newton's synthesis of the apple and the Moon, and the pictures of the cannonball around the Earth as it is launched faster and faster.)
Lose points for distance from Earth, or microgravity if the term is not accompanied by the above explanation. The distance of the Space Shuttle from the Earth is not significant enough to result in a low gravity environment by itself - if we had a platform rising from the Earth and attached to the ground, you could stand on it and still experience gravity. It's only b/c the Shuttle is in orbit that it appears gravity is not affecting you.
Once again, thanks for the help!
X-posted
Regarding the timing issue, everyone reported that it took them a very short time to type their answers - admittedly it's a self-selected group (I doubt slow typers would enjoy blogging all that much, and people who hate science probably wouldn't be answering these questions for me), but still it gives me a starting point. My plan with my class is to (a) ask students during the first week about their typing skills, (b) unless any of their answers worry me, I'll give the same amount of time for the first quiz as I would give in a face-to-face class, (c) I'll look at the statistics of how long it took them to complete the quiz and adjust subsequent quizzes accordingly.
So for the answers, below are what I was looking for, key words/concepts bolded, along with some items that would likely lose the person points and why.
1) Explain the cause of the seasons.
As the Earth orbits the Sun, its axis is tilted by 23.5ยบ. This results in sunlight hitting the surface of the Earth more or less directly (resulting in more or less intense sunlight) depending upon which part of the Earth is pointed towards the Sun at that particular time of year. The tilt also results in the length of the day changing through out the year.
Distance from the Sun would lose you points: the Earth's orbit is so close to circular that the distance does not make any measurable difference in the weather on Earth. Earth is actually closest to the Sun on Jan 3 or so, Northern Hemisphere Winter, Southern Hemisphere Summer - if it were simply distance from the orbit then both hemispheres would have the same season. Saying the tilt makes one part closer to or farther from the Sun is a little more creative (and would gain partial credit from the tilt), but also doesn't make a big enough difference.
2) Is Pluto currently considered a planet by astronomers? Why or why not?
The current definition of planet require an object to orbit the Sun, be small enough to not be undergoing nuclear fusion, be large enough to be round from self-gravitation, and have cleared its orbit. Pluto fails the last criterion, as there are many other objects orbiting just outside Neptune's orbit, variously called plutinos, plutiods, trans-Neptunian objects, and a larger group called Kuiper Belt Objects.
3) Compare and contrast the Greenhouse Effect and the Ozone Layer.
The greenhouse effect is caused by greenhouse gases (such as CO2, H20, CH4, etc.) distributed throughout the atmosphere (or closer to the ground) while the ozone layer is one region of the stratosphere containing O3. The ozone layer acts simply to absorb much of the incoming UV and prevent it from reaching the ground. The greenhouse effect is more complex, as (nearly) full spectrum light hits the ground, some is reradiated as IR, and then the greenhouse gases trap much of the IR light within the atmosphere.
FWIW I know the wording of this question needs improvement. A better wording might perhaps be "Greenhouse Gases and the Greenhouse Effect, and the Ozone Layer and its effects." I typically explain what I'm looking for before giving this quiz question - I usually tell the students this will be the next quiz, and explain that the two are "opposite and complementary." The main thing I'm looking for here is for the students to distinguish that they are two entirely separate phenomena, since the media always conflates them.
4) Why do astronauts in the Space Shuttle experience weightlessness?
As the Space Shuttle orbits the Earth it is moving just fast enough that as the Shuttle (and everything within) falls towards the Earth due to gravity, the surface of the Earth (and the path of their orbit) curves away underneath them by the same amount that they fall due to the gravity. Therefore they are in free fall, or experience weightlessness even though they are still influenced by gravity. (Compare this situation to Newton's synthesis of the apple and the Moon, and the pictures of the cannonball around the Earth as it is launched faster and faster.)
Lose points for distance from Earth, or microgravity if the term is not accompanied by the above explanation. The distance of the Space Shuttle from the Earth is not significant enough to result in a low gravity environment by itself - if we had a platform rising from the Earth and attached to the ground, you could stand on it and still experience gravity. It's only b/c the Shuttle is in orbit that it appears gravity is not affecting you.
Once again, thanks for the help!
X-posted
