What Is the Velocity of a Massless Ping-Pong Ball After an Elastic Collision?

AI Thread Summary
In an elastic collision involving a massless Ping-Pong ball and an infinitely massive paddle, the ball's velocity after the collision can be calculated using the formula v2f = (2 * infinite mass / (infinite mass - 0)) * 20 m/s, resulting in a velocity of 40 m/s. However, the concept of infinite mass complicates the calculations, as it typically leads to nonsensical results in physics. The discussion highlights the importance of frames of reference, comparing the scenario to a ball moving at 20 m/s relative to a stationary wall. Ultimately, the problem raises questions about the applicability of classical mechanics when dealing with infinite quantities. Understanding these principles is crucial for addressing similar theoretical physics questions.
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An "infinitely massive" Ping-Pong paddle moving with a velocity of 20 m/s hits
a "massless" Ping-Pong ball at rest. The collision is elastic. What is the velocity of
the ball after the collision?

i get v2f = (2(infinite mass)/(infinite mass - 0))*20m/s = 40m/s

is this correct?? i don't know why I am doubting myself.. its just a weird question lol
 
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Correct answer. I don't follow your calc, though. Usually it just isn't possible to calculate anything sensible when there is an infinite quantity involved.

This question is really about frames of reference. How is it different from a ball moving at 20 m/s relative to a stationary wall?
 
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