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**Up:** Motion in Two Dimensions
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Projectile motion is a particular kind of 2 dimensional motion. We make the following assumptions:

- The only force present is the force due to gravity.
- The magnitude of the acceleration due to gravity is
|| =
*g*= 9.8*m*/*s*^{2}We choose a coordinate system in which the positive y-axis points up perpendicular to the earth's surface. This definition gives,*a*_{y}= -*g*and*a*_{x}= 0 . - The rotation of the earth does not affect the motion.

**Initial Conditions**:

We choose the coordinate system so that the particle leaves the origin
(
*x*_{0} = 0, *y*_{0} = 0 ) at time *t*_{0} = 0 with an initial
velocity of .

10/9/1997