Question

A yo-yo has a rotational inertia of 810 g·cm2 and a mass of 95 g. Its axle radius is 2.6 mm and its string is 100 cm long. The yo-yo is thrown so that its its initial speed down the string is 1.0 m/s.
(a) How long does the yo-yo take to reach the end of the string?
s
(b) As it reaches the end of the string, what is its total kinetic energy?
J
(c) As it reaches the end of the string, what is its translational speed?
m/s
(d) As it reaches the end of the string, what is its translational kinetic energy?
J
(e) As it reaches the end of the string, what is its rotational speed?
rad/s
(f) As it reaches the end of the string, what is its rotational kinetic energy?
J

Answer 1

Hint: Use conservation of energy, and the fact that the yo-yo is thrown DOWN. Rotational KE is (1/2) I w^2 and
V = r w
where w is the angular velocity and r is the axle radius.