## Chapter 20

## Q. 20.2

## Step-by-Step

## Verified Solution

The work done in pulling the string is 0.5 × 0.3 = 0.15 J and, as no energy is lost in the process, this is equal to the gain in kinetic energy of the top. So the angular speed attained is ω rad s^{-1}, where

\frac{1}{2} × 2.4 × 10^{-5} ω² = 0.15

⇒ ω² = 12 500.

The angular speed is 112 rad s^{-1} correct to 3 significant figures.