Physics Demo Number: 005

Approximate Run Time: 10 min

Energy Conservation Used With Force Resolution For High-Road Low-Road Races

Demo Description

Roll three ball bearings down 3 tracks using resolution-of-forces and energy conservation arguments for an explanation of the results of the race.



Scientific Principles

  • Conservation of Energy

  • Superposition of Motion into Orthogonal Components

  • Judicious Choice of Directions to Resolve Forces Along

  • Can claim real world applications of Sling Shot effects in (1) Race-Car Maneuvers on Banks and (2)Indoor Bike Racing as well as (3) Space Probes

Equipment

  • 3 track stand

  • 3 ball bearings



Equipment Location

  • [G-1-2]-[G-2-2]

Instructions

When one starts the three balls from rest at the tops of their respective launch ramps, one observes that the ball that travels the straight-line path between the uprights always gets there last, relative to the low-road ball , and first relative to the high-road ball.

SUGGESTED EXPLANATION:

Forget about the rolling motion.

Assume the motion to be sliding without friction. The horizontal-track ball obviously moves at constant speed for the entire distance.

By resolving the normal force on the low-road ball into horizontal and vertical components ,one can conclude that this ball’s horizontal component of velocity is always greater than that of the straight-road companion at all times [invoking energy conservation on the uphill part of the low-road ball’s path].

By resolving the normal force on the high-road ball into horizontal and vertical components, one can conclude that this ball's horizontal component of velocity is always less than that of the straight-road companion at all times [invoking energy conservation on the downhill part of the high-road ball path].



  
Writeup created by David A. Burba
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