Purpose:

The purpose of Lab 1 is to learn how to calculate the linear displacement, linear velocity, and linear acceleration of an object in linear motion.

Videotaping:

• Step 1: One person should stand on a balcony or step ladder with a ball and wad of paper. Adjust the video camera by zooming in or out until you can see the drop point and the floor. You should zoom in as much as possible while still being able to see the drop point and the floor.
• Step 2: Once you set the zoom on the camera do not change it. Videotape a meter stick for 5-10 seconds.
• Step 3: Videotape the objects being dropped making sure to release the objects so that they fall straight down. Videotape the activity using a shutter speed of 1/500 sec or higher.  This will eliminate a blurry picture.

Calculations:

• Step 1: Tape a transparency to the television screen. Using the VCR and TV, advance the videotape to the recording of the meter stick. With permanent markers, mark both ends of the meter stick.
• Step 2: View the trials of the objects dropping. Choose the one trial where the objects are least blurry. (Most likely a darker screen and faster shutter speed.)
• Step 3: Push the jog shuttle button on the remote control. Use the outside dial of the jog shuttle control to forward the videotape to the frame where the objects hit the ground. Mark the objects with a permanent marker at that frame.
• Step 4: Place your finger in the indented circle on the jog/shuttle control and go backwards (counter-clockwise) marking the objects after each third frame (third click-one click equals one frame). Continue marking the objects until they reach their release point. (Note: The release point may not fall on a third frame. If this is the case the number of frames from the previous ball marking to the release point should be recorded.)
• Step 5: Remove the transparency and gather a ruler, scientific calculator, and pencil to fill in the table with results. First, measure the distance between the ends of the meter stick in millimeters. You will use this measurement to determine the appropriate scale (convert from video distance to reality distance).
  • For example: meter stick (1m in reality) = 85mm (in video distance)
• Step 6: Measure the distance between each object in millimeters and convert the measurement into meters using the calculation below. This is your displacement.
  • Distance between balls (m) = distance between balls (mm)/meter stick measurement (mm)
  • For example: 22mm/85mm = 0.259m
• Step 7: The video camera records 60 frames per second or one frame each 0.0167 seconds. Using distance in meters and time in seconds calculate the velocity and acceleration of the ball in each frame.
  • Velocity = displacement or v = d
                          time₂-time₁             t
    Acceleration = velocity 2 - velocity 1 or a= v₂-v₁
                                        time₂-time₁                        t

Note: In this specific example we can determine the velocity in the first frame because we know that before the objects were dropped its velocity was zero. We also know the acceleration of the objects in the first frame because if the ball was not moving prior to dropping it, then its acceleration was also zero.

Questions:

1. Which object will hit the ground first?
2. What pattern would you expect the linear displacement values to follow?

  

3. What pattern would you expect the linear velocity values to follow?

 

4. What pattern would you expect the linear acceleration values to follow?

 
 
5. Using Microsoft Excel, make one table and three graphs; one each for linear displacement, linear velocity, and linear acceleration.  Include the two objects on the same graph.  How well do your actual values compared to your expected values.

  


	t = t2-t1	d = p2-p1	d = p2-p1	convert to meters	convert to meters	v = d/t	v = d/t	a = v2-v1            t	a = v2-v1            t
		Softball	Shot Put	Softball	Shot Put	Softball	Shot Put	Softball	Shot Put
Frame #	Change in time	displacement (mm)	displacement (mm)	displacement (m)	displacement (m)	Velocity (m/s)	Velocity (m/s)	Acceleration (m/s²)	Acceleration (m/s²)

 

6. Explain why your actual values and your expected values are different. What possible causes account for this error?