Projectile Motion

Key Ideas:

Motion occurs simulatneously in the X and Y directions
Motion can be analyzed in each direction separately and the results combined (Superposition)
Velocity is constant in the X direction unless otherwise stated (a_x = 0)
Motion in the Y direction is under the influence of gravity (a_y = -9.80)
Same equations used in horizontal and vertical kinematics still apply

Problem Solving:

Projectile motion is treated as two separate problems (horizontal and vertical)
For most problems a variable is solved for in one direction and the value carried into the second direction to solve for the desired quantity

Approach:

Create a table as shown below

X Y

Vo

V

a

s

t
Resolve the initial velocity (if given) into it’s horizontal and vertical components
Determine other values given in the problem, and enter values into the table
Decide in which direction (X or Y) more information is known. This is your starting point
Determine which variable will be common to both horizontal and vertical (usually time)
Solve for the common variable using the direction in which more information is known
Carry the common variable value into the other direction and solve for the desired quantity
If necessary, combine results from horizontal and vertical to find the final result (e.g. final velocity)

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