Angular Velocity — Merry-Go-Round (Worked Example)

Problem

A child on a merry-go-round's edge (radius 2.0 m) moves at 3.0 m/s. What is the angular velocity of the ride?

Given

  • v = 3.0 m/s

  • r = 2.0 m

Find

Angular velocity ω.

Principle

Linear and angular speed are linked by v = ωr — every point on a rigid rotator shares one ω.

Formula

Solution

  1. Rearrange: ω=v/r\omega = v/r

  2. Substitute: ω=3.0/2.0\omega = 3.0 / 2.0

  3. Divide: ω=1.5 rad/s\omega = 1.5\ \mathrm{rad/s}

1.5 rad/s

Unit check

(m/s) ÷ m = 1/s = rad/s — correct.

What this means physically

1.5 rad/s is about one revolution every 4.2 s — a brisk but comfortable ride. A child halfway in (r = 1 m) moves at only 1.5 m/s with the same ω.

Common mistake

Thinking ω changes with radius. On a rigid merry-go-round ω is identical everywhere — it is the linear speed v = ωr that grows outward.