I guess this question was timely, as an article just came out in the refereed journal Animal Cognition
on cats understanding physics. The summary: Cats do indeed seem to understand physics.
"Cats understand the principle of cause and effect as well as some elements of physics. Combining these abilities with their keen sense of hearing, they can predict where possible prey hides. These are the findings of researchers from Kyoto University in Japan, led by Saho Takagi and published in Springer's journal Animal Cognition.
Previous work conducted by the Japanese team established that cats predict the presence of invisible objects based on what they hear. In the present study, the researchers wanted to find out if cats use a causal rule to infer if a container holds an object, based on whether it is shaken along with a sound or not. The team also wanted to establish if cats expect an object to fall out or not, once the container is turned over."
Saho Takagi, Minori Arahori, Hitomi Chijiiwa, Mana Tsuzuki, Yuya Hataji, Kazuo Fujita. There’s no ball without noise: cats’ prediction of an object from noise. Animal Cognition, 2016; DOI: 10.1007/s10071-016-1001-6