Cookie Time!

So taking these pictures took many tries, with a ton of flashes and about two dog treats, but with my dad's help we got them! Because it took so much effort I'm putting four pictures up. Anyway, after playing catch with my dog, Cookie, a dalmation labrador, for how more than 7 years now I finally see that it's actually related to physics! The bright yellow tennis ball is not only an example of a projectile, as when it leaves my dad's hands its path is only affected by the force of gravity, but it is also a great example of inertia! Inertia is Newton's first law, stating that an object remains at rest, or maintains a constant velocity, unless a net external force acts upon it. If not for the force of gravity, the tennis ball would travel toward the ground at a constant velocity, however, it accelerates down to earth at -9.8 m/s^2. The ball also would have proceeded at a constant velocity toward the ground if not for Cookie catching it in her mouth. Cookie acts as another net external force that interrupts the object, in this case the tennis ball, maintaining a constant velocity. If we were playing fetch/catch in space, with no gravity, Cookie would still act as the net external force and interrupt the tennis ball's tendency to maintain a constant velocity.

I wonder if there's any physics in the different colors that are in Cookie's eyes in the 1st, 2nd, and 3rd pictures...Maybe I'll explore that next time! =)