Tracking a Ball

Reflection Questions:

1. Describe the motion of the ball at the apex of its trajectory.

2. What happens to the x-component of the ball’s velocity, vx, as the ball moves horizontally? Does it decrease, increase or remain that same? What happens to the vx vectors? Explain how you arrived at your answers.

3. What happens to the y-component of velocity of the ball? Does the ball’s vertical velocity component decrease, increase, or remain that same? What happens to the vy vectors? Explain how you arrived at your answers.

4. What do changes in velocity vector components tell us about acceleration? Begin this reflection by writing the definition for the average acceleration during a time interval Δt = t2 − t1 in terms of the horizontal and vertical velocity vector components using ˆ i , ˆ j notation.

5. What can you conclude about the nature of the horizontal acceleration of this ball based on your results in question 2?

6. What can you conclude about the nature of vertical acceleration for this ball? Explain your reasoning carefully. Is the direction of change positive or negative? Is there a positive or negative acceleration or no acceleration?

A common AP problem is: Determine the range of a projectile from only the initial velocity and angle of launch.  The short answer is YES. The long answer involves Trig Identites, but fortunately AP only asks to solve this for projectiles with a ∆ y = 0 m (y-y_0 = 0), meaning they are released from the same height.