Help me please. Radian (question 15)

[gcombina]

Homework Statement

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

Answer is D but why??

Homework Equations

The Attempt at a Solution

a) α = Δθ / Δt

Can we please go over each option?

OK looking at option a, it does give me an alpha so I don't know what to think of this. Then it says (Alpha = Change of angle/change in time). This seems to be the formula for "angular velocity" but what is alpha? can we go over this first? what is alpha?

 

[haruspex]

a) and b) are typos. a) should be "$\omega=$" and b) should be "$\alpha=$". $\alpha$ is angular acceleration.
Does the answer make sense now?