Measuring g for Gravity
Students use LEGO MINDSTORMS robots to examine and measure gCopyright 2009 Keeshan Williams, Polytechnic Institute of NYU
Using the LEGO® MINDSTORMS® kit, students construct experiments to measure the time it takes a free falling body to travel a specified distance. Students use the touch sensor, rotational sensor, and the NXT brick to measure the time of flight for the falling object at different release heights. After the object is released from its holder and travels a specified distance, a touch sensor is triggered and time of object's descent from release to impact at touch sensor is recorded and displayed on the screen of the NXT. Students calculate the average velocity of the falling object from each point of release, and construct a graph of average velocity versus time. They also create a best fit line for the graph using spreadsheet software. Students use the slope of the best fit line to determine their experimental g value and compare this to the standard value of g.
A fundamental understanding of the role of gravity is the foundation for many feats of engineering that we see in our everyday lives, such as bridges, buildings, airplanes and boats. This experiment is designed to show how similarly shaped objects, of different weights, have the same acceleration when in free fall. Engineers need a solid understanding of forces in order to predict future behavior of the structures or objects they design.
After this activity, students should be able to:
- Construct a plot of velocity vs. time.
- Propose explanations for the difference in the calculated and standard g.
- Perform basic programming using the LEGO MINDSTORMS NXT software.
- Plot data using spreadsheet software.