though the rate at which strain occurs matters. Brittle materials have low toughness as a result of the small amount of plastic deformation they can endure at any rate. However, ductile materials may behave like brittle materials under high-energy impact, hence the need for this kind of test.

The test conditions are governed by many variables, most importantly:
* the dimensions of the usually rectangular cross section of the sample below the notch;
* the height of the hammer at the start position, determining its velocity