If a yo yo has a speed of 3 m/s at the top of the circle, whose radius is 80 cm, What is its speed at the bottom

the kinetic energy at the bottom is the kinetic energy at the top plus the gravitational potential across the circle

.5 m (Vb)^2 = [.5 m (Vt)^2] + [m g h]

dividing by .5 m

(Vb)^2 = (Vt)^2 + 2 g h

v^2 = 3^2 + [2 * 9.8 * (2 * .8)]