Two Dimensional Motion

1. Two Dimensional Motion AP Physics C

2. Reviewing Projectile Motion Basic Definitions Scalar Quantity – Physical quantities that do NOT have a direction associated with them. Ex: distance, speed, time, temperature, energy, voltage Vector quantity – Physical quantities that have a magnitude and a direction. Ex: displacement, velocity, acceleration, force, field Vector Addition – the combination of vectors accounting for their magnitudes as well as their directions. Trigonometric methods are used to combine vectors. Vector Resolution – the breaking apart of a vector into its (x, y and z) components. Trigonometric methods are used to resolve vectors. Vector Addition by the Component Method – the combination of vectors by first resolving the vectors then combining them to find the sum of the x, y and z components. These sums are then combined to find the resultant vector.

3. Reviewing Projectile Motion Recall that in Projectile Motion, the horizontal motion and vertical motion are independent of each other. That means that the horizontal motion (velocity) has no affect on the vertical free-fall. Projectiles simply accelerate downward with a uniform acceleration (9.81 m/s2) while simultaneously moving horizontally.

4. Three Launching Styles - Style 1(Horizontal Launch from an elevated platform) v0y= 0

5. Three Launching Styles - Style 2 (Upward (from the ground) at an angle) Δy = 0

6. Three Launching Styles - Style 3 (From an elevated platform at an angle)

7. Relative Motion • All motion is relative to something else • ‘relative to’  means ‘from the perspective of’ • Usually motion is relative to the Earth • 2 cars on the highway… • Each Moving at 50 mph in the same direction relative to the Earth • Would have a speed of 0 mph relative to each other • The would be staying right next to each other, having no motion with respect to the other car

8. Another Example • Two cars headed toward each other in opposite direction one with a speed of 50 mph (relative to Earth) and the other w/ a speed of 60 mph (relative to Earth) • 50 mph 60 mph • Will the purple car view the green car moving faster or slower than 50 mph? • Faster, the green car will view the purple car approaching much faster than 50 mph, the purple cars speed relative to the the green car is 50 + 60 =110 mph • This is true b/c whoever the observer is does NOT observe their own motion, in other words everything else is moving but them

9. Parallel and Perpendicular Accelerations When a is parallel (or antiparallel) to v, its effect is to change the magnitude of v, but NOT its direction. For example, if a car is traveling in the positive x-direction and experiences an acceleration in the negative x-direction, the speed of the car will change (but it is still traveling along the x-axis). When a is perpendicular to v, its effect is to change the direction of v but not its magnitude. For example, at a given moment the velocity of a car is northward and the acceleration is westward. The speed of the car will not change, but the direction will (it will turn toward the west). This is the fundamental idea behind circular motion (ahh…memories...good times!)

10. Parallel and Perpendicular Accelerations