Projectile Motion -- Video Analysis

Photo1 of Lab
Photo2 of Lab

As we have talked about, all vectors can be broken up into its vertical component (up and down) and its horizontal component (back and forth). This is how we will analyze projectile motion. The horizontal component of the motion of the projectile is the same as constant velocity linear motion in that the projectile travels equal distances in equal time intervals. Because the horizontal motion has a constant velocity its acceleration is zero. The vertical component of projectile motion is a little more complex since this component experiences the acceleration due to gravity or as we know it "g".

In this experiment we will analyze the motion of a ball by videotaping the motion and then looking at the motion frame-by-frame. Video works by taking 30 pictures every second and then playing them. The way that you perceive the motion is that each frame shows the advancement of time by 1/30th of a second. We will analyze the motion by videotaping a ball being thrown in the air and then analyzing the position of the ball in each frame.

Part 1: Depending on how many TV's and VCR's we have we will break the lab into groups. Each group will then video the flight of a projectile. Make sure the video shows a large portion of the total flight so that you will have around ten different frames to analyze the flight of the ball.

Part 2: Now put this videotape into the VCR and locate where the ball is just released and stop the tape (you may need my help to show you how to stop the tape and frame advance it). Using some masking-tape mark the ball on the screen at the point right where its is released or as close to it. Now advance the tape by one frame. Notice that the ball has moved some. Again mark the position of the ball with some tape. Continue to do this for each frame advance until you no longer can see the projectile. The tape on the screen should now show the path of the projectile. Draw below what this path looks like.

Part 3: Now using a ruler measure the horizontal distance between each piece of tape and write down your data. Do you see a pattern in the data, and if so what is it? Explain why this pattern occurs.

Part 4: Now do a similar measurement for the vertical distance between each piece of tape. Again, do you see a pattern and what is it? Explain why this pattern occurs.