Because is constant, the speed will be greater or lesser depending on the magnitude of. To
determine where the speed is least or greatest, we follow the same method as we would with the
one-dimensional example we had in the previous section. That means that the speed of the
projectile in the figure above is at its greatest at position F, and at its least at position C. We also
know that the speed is equal at position B and position D, and at position A and position E.
The key with two-dimensional motion is to remember that you are not dealing with one complex
equation of motion, but rather with two simple equations.
Key Formulas
Average Speedaverage speed =Average
Velocity
average velocity =Average
Acceleration
average acceleration =One-
Dimensional
Motion with
Uniform
Acceleration
(a.k.a. “The
Five Kinematic
Equations”)Velocity of Two-
Dimensional
Projectiles