Video Measurement of Position vs Time
- Gather data using an motion analysis application.
- Learn how to make a position vs time graph.
- Calculate average velocity using the data and graph.
- Ring stand with utility clamp
- Ping-pong ball (or equivalent)
- Meter stick (to measure position)
- V-shaped plastic molding (used as a ramp to guide the ping-pong ball)
- iPad with SmartMotion app.
- Work with your team to gather the data. Each person records the data and does calculations!
- Use the ring stand utility clamp to hold an end of the plastic molding about 10cm off the table (The ramp should not be too steep).
- The other end of the V-shaped plastic molding can rest on the table top.
- Place the meter stick at the end of the plastic molding in the ball run-out zone.
- Test Stand Top View
Ring Stand end middle begin _____ v v v ramp | | ==============================O | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |____| meter stick
- Release the ping-pong ball at the top of the ramp.
- Use the ipad camera to capture a video of the ball as it rolls off the ramp and across the table.
- Capture the first ≈30 cm of travel across the table.
- Open the video in SmartMotion.
- You may use the frame set feature to narrow down the part of the video you are most interested in.
- Use the Next and Previous frame buttons to select the frame as the ball just leaves the ramp.
- Record the beginning distance and time. If the ball is a blur select one portion of the blur as your point for measuring the first and last frame.
- Use the Next and Previous frame buttons to select the middle frame you want.
- Record the middle distance and time.
- Use the Next and Previous frame buttons to select the last frame you want.
- Record the ending distance and time.
|Location on table||Position (cm)||Time (s)|
- Use UDRSS to calculate the beginning ball speed (beginning to middle).
- Use UDRSS to calculate the ending ball speed (middle to end).
- Use UDRSS to calculate the overall ball speed (beginning to end).
- Is the beginning speed faster than the ending speed? Does this make sense?
- Why would you expect the overall speed value to be in between the beginning speed and ending speed? Do your measurements fit this pattern?
- Graph the time vs position. Time = x-axis.