Gears: Determining Angular Velocity
Students preparing the robot to determine angular velocity.Copyright 2010 Jennifer S. Haghpanah, Polytechnic Institute of NYU
Students work as engineers and learn to conduct controlled experiments by changing one experimental variable at a time to study its effect on the experiment outcome. Specifically, they conduct experiments to determine the angular velocity for a gear train with varying gear ratios and lengths. Student groups assemble LEGO® MINDSTORMS® EV3 robots with variously sized gears in a gear train and then design programs using the EV3 software to cause the motor to rotate all the gears in the gear train. They use the LEGO data logging program and color sensors to set up experiments. They run the program with the motor and the color sensor at the same time and analyze the resulting plot in order to determine the angular velocity using the provided physics-based equations. Finally, students manipulate the gear train with different gears and different lengths in order to analyze all these factors and figure out which manipulation has a higher angular velocity. They use the equations for circumference of a circle and angular velocity; and convert units between radians and degrees.
The concept of angular velocity is used in engineering applications every day, from car wheels to orbiting spacecraft. The magnitude of angular velocity is the angular speed of an object as it rotates about a specified axis, measured in radians per second. An understanding the angular velocity of objects can be used to determine how fast something rotates and to derive the angular acceleration, which can be used to determine the torque exerted on a body. One way of changing the angular velocity and the torque is by the use of gears. Mechanical engineers utilize gears in drive trains for a variety of applications ranging from bicycles to automobiles. Gears are used to transmit power, change the direction of power and alter the angular velocity and torque being applied to the output of a system. The angular velocity or torque can be modified by changing the gear ratio.
In this activity, students learn to design a setup for engineering experimentation. Specifically, they design their own robots, write their own robot programs and determine angular velocities. As they play with changing the robot design, they figure out what design features help increase angular velocity; they optimize angular velocity by changing gears and number of gears, and use the provided equations.
After this activity, students should be able to:
- Design a LEGO MINDSTORMS EV3 robot with a gear train.
- Program a LEGO robot using the EV3 software.
- Design a gear train with two different types of gears with a specified number of gears.
- Calculate the angular velocity of rotating gears using a color sensor to detect wheel rotation.
- Change one variable at a time and examine its effect on angular velocity.