[The Second Blog] Projectiles.

     This week, we extended our knowledge of position, velocity, and acceleration into two (and even three) dimensions with the lesson on projectiles.  A projectile is an object projected, for lack of a better word, into space that, once released, is only influenced by the force of gravity. The motion of a projectile can be seen as my brother shoots a basketball. Today he just so happened to be doing so—in the living room (but at least he didn’t hit anything).  I don’t generally pay attention to him when he’s practicing – he wouldn’t want me to, anyway – but since I could relate it to our physics concepts, I decided to observe for a second.

[General graphs depicting
projectile motion]

     Being that it is a projectile, when the basketball is shot into the air, it moves in a parabolic path. This is due to the fact that the only force acting on the ball, assuming no air resistance, is gravity. Therefore, in the y-dimension, because of the acceleration of gravity – a constant –9.8 m/s² – acting on the ball, position follows a curved path, increasing initially then decreasing to form the shape of a parabola, with velocity decreasing (in the positive direction) from the time the ball is released until the time that it reaches the peak of its trajectory and increasing (but in the negative direction) on its way back down after reaching the peak. In the x-dimension, though, because there are no forces, position increases at a constant rate, velocity remains constant, and thus acceleration is zero.