Q. 6

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Found in: Page 566

### Physics for Scientists and Engineers: A Strategic Approach with Modern Physics

Book edition 4th
Author(s) Randall D. Knight
Pages 1240 pages
ISBN 9780133942651

# A lottery machine uses blowing air to keep 2000 Ping-Pong balls bouncing around inside a box. The diameter of a Ping-Pong ball is . What is the mean free path between collisions? Give your answer in.

The mean free path between collision is .

See the step by step solution

## Step 1: Given Information

Number of Ping-Pong balls in a lottery machine

Lottery machine dimension

The diameter of a Ping-Pong ball

## Step 2: Explanation (Part a)

Due to collisions with other molecules, a molecule undergoing distance travel experiences a delay between diffusing to a different position due to these collisions.

The molecules need a certain amount of time to diffuse to a new position.

In equation (20.3), the mean free path is the distance the molecules travel between collisions on average.

The number density is given by equation,

number of particles

volume of the box.

To calculate the volume,

Use equation (2) to get number density,

Diameter of the ball ,

Put the values for and into equation (1) to get ,