The magnitude of centripetal acceleration for an object moving at speed v on a circle of radius r can be written which two equivalent ways?

1. Starting from the similar-triangles argument, centripetal acceleration comes out as speed squared divided by radius, ac = v^2 / r. 2. Substituting v = r*omega into that expression gives ac = (r*omega)^2 / r, which simplifies to ac = r*omega^2. 3. Both forms describe the same acceleration, one written in terms of linear speed and one in terms of angular velocity. 4. The other listed combinations either use the wrong power of v or omega, or invert the role of the radius, so they do not reduce correctly from the similar-triangles derivation. _Source: OpenStax College Physics (CC BY 4.0), Ch 6 "Uniform Circular Motion and Gravitation", section 6.2 Centripetal Acceleration_