# Can someone explain this to me please?

1. Dec 9, 2014

### gcombina

1. The problem statement, all variables and given/known data
Which equation is valid only when the angular measure is expressed in radians?
a) α = Δθ / Δt

b) ω= Δω / Δt

c) ω^2 = ωo^2 + 2αθ

d) ω = Vt/r (here T is a subscript)

e) θ = 1/2αt^2 + ωαt

2. Relevant equations

I know angles can be measured in either degrees or radians

3. The attempt at a solution

angular velocity = ??? divided by radius

I guess I don't understand what Vt is

2. Dec 9, 2014

### Vagn

How do you relate the length of an arc to the angle subtended by the arc and the radius? What should the units of each quantity be?

3. Dec 9, 2014

### Staff: Mentor

Presumably $V_t$ will be defined in the text surrounding the problem. In this context I would imagine that it represents the tangential velocity of a rotating object at distance r from the center of rotation.