A wheel of radius R starts from rest and accelerates with a constant angular acceleration alpha about a fixed axis. At what time t, will the centripetal and tangential accelerations of a point on the rim have the same magnitude?

Answer 1

When alpha*R = V^2/R = (R*alpha*t)2/R
alpha*R = R*(alpha*t)^2

1 = alpha*t^2

t = 1/sqrt(alpha)

(independent of R)