An interesting experiment on density is to have a helium balloon loose in your car while driving. Gravity is an acceleration, not a force, just like the effects of accelerating, braking, or cornering. The kewl thing is while you're turning hard to the left, while you feel your bodies being "pushed" to the right, the helium balloon will go the opposite way, due to its density relative to everything else in the car. Accelerate and the balloon will rush up the the front, brake, and it will go to the back.
Prolly more interesting to a kid than a squirrel though.
Are we off topic yet?