Cavendish Gravity Experiment: A Setup Modification

Format

SOECS Senior Project Demonstration

Abstract/Artist Statement

One of the experiments performed in the Advanced Physics Laboratory course offered by the University of the Pacific Physics Department is the Cavendish Gravity experiment. This experiment is designed to measure the universal gravitational constant, which relates gravitational attraction between any two objects and the mass of the objects. Using a "Gravitational Torsion Balance", a system of masses is rotated due to gravitational attraction. To measure this rotation, a laser beam is reflected off a mirror mounted on the system of masses and projected onto a screen or wall. Our addition to this experiment is a system to capture the position of the laser beam as a function of time. Using a webcam, we were able to track the laser beam and pass that information into a computer. A program was written to translate webcam information into position and to provide a user interface. In addition, a blue screen was built to aid in capturing the laser position. This allows us to make sure that the only red in the image captured by the webcam is from the laser, making it easier to track. The screen also includes a set of green LEDs that are placed a set distance apart to help translate the position that the webcam reads, which is in pixels, to the actual position in centimeters. Now that we have made this addition to the Cavendish Gravity Experiment Apparatus, it can be used in future offerings of the Advanced Physics Laboratory course.

Location

School of Engineering & Computer Science

Start Date

2-5-2009 2:00 PM

End Date

2-5-2009 3:30 PM

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May 2nd, 2:00 PM May 2nd, 3:30 PM

Cavendish Gravity Experiment: A Setup Modification

School of Engineering & Computer Science

One of the experiments performed in the Advanced Physics Laboratory course offered by the University of the Pacific Physics Department is the Cavendish Gravity experiment. This experiment is designed to measure the universal gravitational constant, which relates gravitational attraction between any two objects and the mass of the objects. Using a "Gravitational Torsion Balance", a system of masses is rotated due to gravitational attraction. To measure this rotation, a laser beam is reflected off a mirror mounted on the system of masses and projected onto a screen or wall. Our addition to this experiment is a system to capture the position of the laser beam as a function of time. Using a webcam, we were able to track the laser beam and pass that information into a computer. A program was written to translate webcam information into position and to provide a user interface. In addition, a blue screen was built to aid in capturing the laser position. This allows us to make sure that the only red in the image captured by the webcam is from the laser, making it easier to track. The screen also includes a set of green LEDs that are placed a set distance apart to help translate the position that the webcam reads, which is in pixels, to the actual position in centimeters. Now that we have made this addition to the Cavendish Gravity Experiment Apparatus, it can be used in future offerings of the Advanced Physics Laboratory course.