Module 2—Motion in Two Dimensions
Lesson Summary
In this lesson you explored the following essential question:
- How can independent vertical and horizontal motions be analyzed with kinematic equations to predict the two-dimensional position and velocity of a projectile at various times?
Principle of Projectile Motion
The projectile motion of an object subject to no air resistance is a combination of two motions: a horizontal motion with a constant velocity equal to the object's initial horizontal velocity and a vertical motion with a constant vertical acceleration (gravity).
For projectile motion, when an object is thrown at an angle from the ground (Figure A) or projected horizontally off of a table or a cliff (Figure B), the principle of combining independent motions applies. The vertical component of motion is being affected by the acceleration of gravity, while the horizontal component is not affected by gravity. The result is that the object follows a parabolic path or trajectory. A parabolic path results because the projectile is falling due to the attraction of gravity and, at the same time, it is moving horizontally with constant velocity.
Lesson Glossary
independent: not affecting one another
initial velocity: the velocity of an object when an experiment begins
parabolic: an arched shape having the form of a parabola
projectile: a moving object acted on by no forces other than gravity