Experiment 2 ~ Projectile Motion
Purpose:
In this experiment, you will study projectile motion, and see how to separate the motion of a
projectile into its x and y components.
Two photographs (a double exposure) using a digital camera and strobe light illumination will
enable you to get a picture of the trajectory of a ball as it is tossed between you and your lab
partner. One of the exposures will show you a grid from which you can calculate the ball’s
position; the other exposure will show you the ball’s trajectory. The combined exposures will
show you the ball at various instants during its trajectory superimposed on the grid. You can then
compare the measured trajectory with what you would expect based on the equations discussed
in class.
Equipment:
Strobe light, Digital camera and printer, 100cm X 100cm grid, black felt cover, golf ball, and
flash drive (optional)
Procedure:
You and your lab partner should practice tossing the ball back and forth before you have the lab
instructor take the photograph. Make sure that the ball’s trajectory arches completely within the
grid – not going above the top of the grid, and not traveling in a straight line horizontally across
the grid.
Two pictures will be taken by the lab instructor. The first will be of just the grid, with the
room lights on. The second photograph will be superimposed over the first, and taken with the
overhead lights out and strobe light on. The shutter on the camera will be held open while you
toss the ball in front of the grid. The photo will then show the ball’s trajectory, i.e., its position
at equal time intervals, (1/flash rate), superposed on the grid. A good photo should have at least
five clearly defined images.
Be sure to record the flash rate from the strobe light! (It should be 14 -17 flashes/second).
The photo will be sent to the printer and a digital copy can be stored on your thumb drive to be
printed in your lab report.
