QI. A student is swinging a 200 g yo-yo on a 1.0 m long string. How fast must the yo-yo be moving at the bottom of the circle to reach the top
of the circle with no speed?

Consider a small frictionless puck perched at the top of a fixed sphere of radius r. if the puck is given a tiny nudge so that it begins to slide down, through what vertical height will it descend before it leaves the surface of the sphere? [hint: use conservation of energy to find the puck's speed as a func e conservation of energy to find the puck's speed as a function of its height at what value of this normal force does the puck leave the sphere? ] here on the puck.