Re: Vectors, and scalors

Dear Gabe,

Yes, any horizontal motion an object might have doesn't affect its vertical acceleration due to gravity. It'll take the same time to hit the ground regardless of whether it drops from rest, from a car moving at 100kph, or from a jet moving at 1000kph (long as they're all at the same height). One important detail, though, is that this _only_ works over scales small enough that the curvature of the Earth doesn't become a factor. Throw something _far_ enough, and the ground will curve out from beneath it! In fact, with enough horizontal velocity, the curve of the falling object will be exactly parallel to the curve of the Earth's surface -- so the object won't get any closer to the ground at all. That's what an orbit is, so you could put a baseball into a very low orbit just by pitching it at the right speed (I'm ignoring the air resistance to make a point about orbit, but of course in real life the air resistance would slow the ball down quickly, so it'd drop back to Earth before it got too far... and in fact would probably burn up from friction!)

I'm including a diagram from the U Cal Berkeley demonstration collection which shows the kind of equipment you were asking about. Their location is http://www.mip.berkeley.edu/physics/noteindex.html#projectiles

Hope that helped,
Jim Moskowitz
The Franklin Institute
jimmosk@fi.edu