As well as knowledge structures can be complex and coherent, they might be small and disconnected. This study focuses on knowledge elements of pre-service teachers using diSessa's phenomenological primitives (p-prims) framework. Based on group interviews, a test was developed regarding the knowledge fragments used for explaining free fall in three different contexts--the Earth, the Moon, and Mars--for both vertically released and kicked balls. The test was then implemented to 274 pre-service primary teachers. The results indicated that teacher candidates used six different p-prims such as force as a mover, closer means stronger, bigger is greater, overcoming, dynamic balance, and dying away to explain free fall. The use and appropriateness of p-prims differed due to context both qualitatively and statistically.