# The dominance of Gravity vs Strength and its dependency on crater size

So I am trying to write a research paper (about 3700 words) for high school about the topic "The dominance of Gravity vs Strength and its dependency on crater size" or something similar.

I have found the following information which I am struggling to understand and has been holding me back from continuing the research : (Can someone explain what dominance is and how can I approach reading more about this topic?)

• Making a crater requires both material strength of the target and gravity to be overcome.
• which of these dominates depends on the size of the crater

$$\rho g d = \frac{1}{5} \rho g D = Y$$

Where Y is the yield strength, ρ is density of the target material, d is the crater's depth and D is its diameter.

A related graph to this topic is this (Holsapple 1993) :

So please, can someone explain what all this means in simple terms ?

## 2 Answers

I guess the point is that there are two ways to calculate how big a crater a given impact will create. One is based on calculating how much rock the impact energy can shatter so the main constraint is the strength of the rock) the other on calculating how much it can lift (so the main constraint is the weight of the rock). For small impacts the first is the main consideration ("dominates") for large impact's its the second and the formula identifies the point around which it changes over.

Dominance is not a technical term. To give another example, when riding a bike fast on level ground, we might say that wind resistance is the dominant force, but when riding slowly uphill gravity is dominant.