IIIA. CRATER SIZE


Note: This activity is written for two levels.
Level one is appropriate for pre-algebra students, and
level two involves more sophisticated algebra skills including the manipulation of an equation with two variables.


[see "Just how big is big?" in Craters!]


Concepts (Level One):

Crater Size (Level One)


Crater size is related to the mass and velocity of the impacting body. Mass and velocity can be combined to find the kinetic energy of an impactor. Increasing either the mass or the velocity of the impactor increases the kinetic energy of the impact. Review the results of your crater experiments in section IIA. The size of the crater increased with the mass of the bolide, and also with the height from which it was dropped (which is proportional to the speed of impact). This fundamental physical relationship allows an estimate of impactor mass to be made from crater diameter.


Activity:




Concepts (Level Two):


Crater Size (Level Two)

Crater size is related to the size and velocity of the impacting body. These two quantities can be combined to find the kinetic energy of an impactor, defined as

K = 1/2 m v2

where K is the kinetic energy, m is the mass of the impacting body, and v is the velocity of the impactor. Review the results of your crater experiments in section IIA. The size of the crater increased with the mass of the bolide, and also with the height from which it was dropped (which is proportional to the speed of impact). This fundamental physical relationship allows an estimate of bolide mass to be made from crater diameter.


Activity:

Measuring the diameters of craters allows us to estimate the size of the impacting bolide. The diameter is proportional to both the mass of the bolide and its impact velocity. We can measure the estimate the size of the impacting bolide. The diameter is proportional to both the mass of the bolide and its impact velocity. We can measure the diameter of the crater, but unless we know either the mass or the velocity of the bolide, we can't solve for the other. By assuming a constant impact velocity, however, we can predict relative bolide masses for different crater diameters.




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This module was written by Cynthia Phillips, Dept. of Planetary Sciences, University of Arizona, Tucson AZ, and funded in part by the NASA Spacegrant program.


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