There are multiple concepts that come into consideration when discussing Projectile Motion. Recently, our class (period 1/2) discussed Vertical Velocity (VY), and Horizontal Velocity (VX).
A projectile's horizontal velocity is constant, and has an acceleration of 0. This is due to the fact that there are no substantial forces acting on the object in the horizontal direction. The only horizontal force acting on the object would be air resistance, and in most cases, this force is negligible (i.e. a small steel ball). Because V(sub X) is constant, it's initial velocity is the same as its horizontal velocity at any point in time (unless the object has stopped).
A projectile's vertical velocity has constant acceleration. The earth exerts a gravitational force upon the object that pulls the object towards the earth with a constant acceleration of about 10 meters every second. This is why the object eventually stops moving (in general). The earth's gravitational force brings the object towards it. and the object eventually hits a surface that stops it's motion.
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1 comments:
cornelius--this is a great post. My only additional comment is that the projectile is never stopped by gravity. It's vertical velocity is zero for an instant as it switches from moving up to moving down, but it doesn't stop (which would imply zero acceleration).
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