Revisiting the Feynman Ball on an Inclined Plane Problem

Thread starter John Helly
Start date Jul 7, 2023
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Ball Feynman Inclined

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The discussion centers on the correct calculation of forces acting on a ball resting on an inclined plane against a vertical wall. Participants debate whether the force exerted on the wall (Fw) should be calculated using Fw = sec(alpha) * kg-wt or Fw = tan(alpha) * kg-wt. Initially, there is confusion about the correct expression, but it is ultimately clarified that the published solution is correct. The importance of accurately drawing free-body diagrams and applying Newton's laws to resolve forces is emphasized. The conversation concludes with a focus on ensuring proper understanding of vector components and their signs in the context of static equilibrium.

Jul 11, 2023

kuruman

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I concur with @TSny. For future reference, when the sum of any number of vectors is zero and you add them using the graphical "tip-to-tail" graphical construction, you end with a closed polygon. The number of sides is equal to the number of forces that are added.

Here you have a right triangle because there are 3 forces and ##F_w## and ##F_g## are perpendicular (see below). All you have to do is figure out which of the interior acute angles should be labeled ##\alpha## and then write down the usual trig relations.