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

In summary, the conversation discusses the elastic collision between an "infinitely massive" Ping-Pong paddle moving at 20 m/s and a "massless" Ping-Pong ball at rest. The question at hand is what the velocity of the ball will be after the collision. The answer is determined to be 40 m/s, but there is some doubt and confusion due to the involvement of infinite quantities and varying frames of reference.
  • #1
EndoBendo
11
0
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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  • #2
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?
 

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

1. What is an elastic collision?

An elastic collision is a type of collision between two objects in which both the momentum and kinetic energy are conserved. This means that the total kinetic energy before the collision is equal to the total kinetic energy after the collision.

2. How is the momentum conserved in an elastic collision?

In an elastic collision, the total momentum of the system (both objects) before the collision is equal to the total momentum after the collision. This is due to the fact that there is no external force acting on the system, so the total momentum remains constant.

3. How is the kinetic energy conserved in an elastic collision?

In an elastic collision, the total kinetic energy of the system before the collision is equal to the total kinetic energy after the collision. This is because the kinetic energy is dependent on the objects' masses and velocities, which remain constant in an elastic collision.

4. What is the equation for calculating the velocity of objects after an elastic collision?

The equation for calculating the velocity of objects after an elastic collision is: vf = (m1 - m2)u1 / (m1 + m2), where vf is the final velocity, m1 and m2 are the masses of the two objects, and u1 is the initial velocity of the first object.

5. Can an elastic collision occur between objects of different masses?

Yes, an elastic collision can occur between objects of different masses. As long as the kinetic energy and momentum are conserved, the masses of the objects do not affect the occurrence of an elastic collision.

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