Children are not blank slates when they begin school; instead, they bring prior conceptions about the everyday world with them. Situations of motion are ubiquitous in everyday life, and because of much interchange with the physical world conceptions are affected from a very early age. Yet prior conceptions of motion usually do not comply with accepted scientific views, and therefore conceptions need to be changed within the course of education. A differentiation can be made between explicit declarative knowledge and tacit procedural knowledge. 144 children aged 4 to 11 years were assessed on their explicit understanding of object speed and speed change along a horizontal, down an incline, and in free fall. Study 1 assessed the children’s predictions of motion using a range of everyday objects. Their conceptions were further assessed in Study 2 using a tube and two balls of different weights. Study 3 was a computer-presented quasi-replication of the tube-and-balls study. The results of these three studies suggest that children’s explicit predictions of motion are limited or incorrect. At the same time, many infancy studies have unveiled underlying knowledge about the physical world, which is considered tacit in its nature. Some researchers posit the idea that this knowledge does not change at its core and persists throughout the lifespan. While infancy research methods would be difficult to apply in a sample of children, judgement tasks may help in tapping tacit understanding in this age range. In Study 4, the children were shown video clips of the same set-up used in Study 3 but with motion occurring, either correctly or incorrectly. The children had to judge whether what they saw in the clips looked correct or not. The results indicate a mismatch between tasks requiring explicit predictions and a task relying on tacit judgements, suggesting judgements are more accurate than predictions. A dual-pathway model incorporating explicit and tacit reasoning is proposed, limitations of the current work are discussed, and suggestions for future work are made. Overall, it is evident that two kinds of understanding about the same topic are available in young children, and it is hoped that early science education can eventually consider this differentiation in order to facilitate conceptual change.