## Wednesday, November 3, 2010

### Which One's Best?

Two questions:

1.  Is the question clear?
2.  Which image asks it best?

#1

#2

#3

Anonymous said...

I'm wondering if my years of indoctrination with physics are skewing my opinions--disclaimer given, moving on. I think the natural question that students might ask is: which one will hit the ground first?

I like picture number 2 best. It's easier to see the similarities in how the drop distances change with both balls than in the first one. Unless the fact that the yellow ball hits the other building is something you want students to investigate, I would avoid picture 3. It might complicate things in ways you don't want at the start of the investigation.

CalcDave said...

I didn't notice the ball that's just dropped at first, so my question was, "Will the yellow ball land on the other building?" For that, picture 1 was the best.

Having seen the 2nd ball and the rest of the pictures, I kinda agree with betweenthenumbers. Although, it seems clear from even the first picture that the yellow will land first, so I don't know that I'd actually ask that question, since the answer seems obvious.

So, I'm not sure if I'm any help, but it doesn't seem to ask much of a question to me. It seems to illustrate the physics concept of gravity and clearly shows how the motion is parabolic in nature, but it almost seems TOO obvious to ask a good question.

I don't think I could not use picture 3, though. I like how the ball hits the other building and is flat. Even if it was just a follow-up after using 1 and/or 2.

Dan Anderson said...

Which ball hits first is difficult to measure because of the camera position. Because the angle it looks like the yellow should hit first, even though it appears to have started out moving upwards a bit.
I suppose it depends on the question, but I too like picture 2 the best. Plenty of mystery left, but enough data to get a good grasp of the material.

Dvora C said...

I think picture 2 asks best which will hit the ground first? The first one it is hard to tell that the green ball is dropping straight down.

Anonymous said...

a. I hate you for your weather right now.

b. I know the first question is going to be which hits the ground first. That may be quickly figured out by reasoning, not calculation.

c. No matter what the question is, I like #2 the best. You can see that the vertical displacements are equal and increasing with each step. It's just enough to put some doubt into a hand waving argument.

Anonymous said...

Did you just recreate "shoot the monkey" for physics? (http://www.fas.harvard.edu/~scdiroff/lds/NewtonianMechanics/ShoottheMonkey/ShoottheMonkey.html) If so, I like image 2 best. Like the others have said, showing the ball hitting the other building only complicates things (unless that's the point, too).

Anonymous said...

I thought the question was "can you determine the camera position and angle then apply the perspective transform to get an orthogonal view from this perspective-distorted image?"

Or maybe the problem is to derive the formula for acceleration in free fall?
The ball is obviously going to hit the ground, but who cares?

David Cox said...

I think that the perspective definitely is misleading here. The answer is not as obvious as you may think. Does that ruin the problem or add more to it? I'm not sure yet. I'll post he question in video format and see if that helps.

@hillbyCan't apologize for the CA weather in the fall. Sorry boutcha.

I've never seen the "shoot the monkey" kalamatiykat. Thanks for the link.

@ gasstationwithoutpumps
I'm sure that there is some feedback in your comment, but forgive me for not catching it.