In the blink of an eye, illustrate important concepts such as torque, acceleration and center of mass with this discrepant event demonstration. A stick with a cup near one end and a hinge at the other is propped at an angle with a support rod. A ball is placed on the end of the stick so that the ball is below the lip of the cup. The support rod is swiftly pulled out, the ball and stick fall simultaneously, resulting in the ball landing in the cup! Did the stick really fall faster than the free-falling ball? After students study the apparatus they will recognize that the stick does not actually “free fall.” The stick rotates as it falls because of the hinge, and this causes the end of the stick to accelerate faster than its center of mass, allowing the end of the stick to beat the ball to the ground. This economically designed apparatus is easy to set up.
Concepts: Acceleration due to gravity, torque, rotational acceleration, center of mass.
Time Required: 15 minutes
Materials Provided: Clamp with bracket, clay, support stick, foam block, rubber band, stick with cup and hole, Velcro®-covered ball.
Note: A support stand is required and available separately.
Additional ResourcesNo Additional Resources at the time.
Flinn Catalog/Reference Manual Page 633
Flinn Middle School Catalog/Reference Manual Page 282
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