how does size and velocity affect meteor crater patterns?

[codys740]

Hello my name is Cody Slone, I'm and working on m science fair project about meteor crater patterns and I'm having some issues figuring out about the physics factor that affect my project..

[deleted-2574]

Hi Cody,

If you provide "how does size and velocity affect meteor crater patterns?" to answers.com, you'll get back many resources.

The first hit from answers.com includes the Sci-Tech Dict. and Wikipedia entries for impact crater.
The second hit from nasa.gov includes a sample crater project.
The third hit from answers.com collects information on meteorites from a variety of sources.
The sixth hit from lessonsplanet.com gives crater related science projects arranged by grade level.
The eighth hit from crystalinks.com gives general crater information and has many links to explore.

Re: the physics factors, if you provide "what is the physics of meteor impacts?" to answers.com, the output is not as rich as the output above.

The second hit from alaeo.gly.bris.ac.uk may provide the information you're looking for, or you may need to vary the input to answers.com.

Please post again if you have any questions.

[deleted-2131]

Hi Cody,

I'm excited about your question! My personal research interests are related to impact cratering, particularly looking at the chemistry involved in impacts, so I would be happy to help you as you work on your project. The physics that relate to impact cratering on a planetary scale are quite complex, but for your project, I think that some basic equations will suffice.

First, you need to understand the difference between gravitational potential and kinetic energy and how they relate to each other. Is this something you have talked about in your science class? Here's the important concept: The height at which you drop your "meteor" (gravitational potential energy) will affect how fast it is going when it crashes into your target (and thus the kinetic energy with which it strikes the target). As the "meteor" collides with the target, the kinetic energy that the "meteor" had is transferred to the target material, causing it to be excavated (thrown up into the air) and then deposited again. This is a simplified view of the process the leads to the formation of the crater.

Planetary scientists usually refer the process of impact cratering in three steps: the contact and compression phase, the excavation phase, and the modification phase. In your experiments, the contact and compression phase will take place as the "meteor" hits the target, the excavation phase will take place as the target material is thrown up into the air, and the modification phase will take place as the material that was thrown into the air falls back down. All three of these steps will happen quickly enough that you might not be able to really tell them apart.

If you are interested in some of the mathematics that you can use to analyze the experiment, read on! Don't be scared of the math; it's all just multiplication, division, and some exponents. If you don't know about exponents, then don't worry about this section; however, if you want to take your project to the next level, this sort of mathematical analysis will be helpful. If you don't want to worry about this math, then just skip ahead to where it says "End of Messy (But Fun!) Math Section".

An equation that you will probably find useful is that the diameter of the crater is proportional to the cubed root the kinetic energy of the "meteor" at the time of impact. That is, D ~ E^(1/3). You can determine the kinetic energy the "meteor" will have at the time of impact by using the equation KE = (1/2)mv^2 where KE stands for kinetic energy in Joules, m is the mass of the "meteor" in kilograms, and v is the velocity of the "meteor" in meters per second.

Note that the equation for kinetic energy has both mass and velocity in it. Your question is "how does size and velocity affect meteor crater patterns?" The size of your "meteors" will be related in some way to their mass, so this equation encapsulates some of the fundamental physics behind your project.

In order to find the velocity (you can think of velocity as speed for your purposes) of the "meteor" just before it hits the target, you will need some basic kinematics equations. The kinematics equations allow you to describe the motion of an object. In your case, I am guessing that you will drop your "meteors" from a certain height. If you know the height from which you drop the "meteor" (in meters), you can calculate the velocity the "meteor" will have just before it hits the target by using the equation (vf)^2 - (vi)^2 = 2ad where vf is the final velocity in meters per second (the number you want to solve for to plug into the equation for kinetic energy), vi is the initial velocity (in meters per second), a is the acceleration due to gravity (in meters per second squared), and d is the height of the "meteor" above the ground (in meters). Since the "meteor" is being dropped from rest (it isn't moving before being dropped), vi is 0. a = 9.8 m/s^2. So...drum roll... vf = Sqrt(19.6d)!

So, to summarize what this mathematical adventure has taught us: if we know the height from which you drop the "meteor", you can calculate the velocity that the "meteor" has just before impact. This, in turn, allows to calculate the kinetic energy of the impactor (assuming you know its mass). And once we know the kinetic energy of the impactor, we approximate the diameter of the crater! This data analysis approach will allow you to analyze your data in a rigorous way, helping to reveal the answer to your question. This sort of analysis would be very sophisticated for a 6th grader, but probably wouldn't be beyond the abilities of an 8th grader.

END OF MESSY (BUT FUN!) MATH SECTION

I know that this has been a lot of material to digest - you asked about the physics affecting your project and I wrote you a rather detailed response; read through it and then let me know the parts you don't understand, and I will explain them better. If you're interested in the math, let me know and we can explore that further. If you're not interested in the math, that's fine, too; just let me know.

Keep the questions coming! You've got a great question with a lot of potential; I'm excited to see how things work out for you.