Circular Motion Practice

Key Equations F r = ma r a r = v 2 /r Note (s): When circular motion is constant, the net force is always toward the center! So F net = F r Always assign the positive direction in the direction of the acceleration. (i.e. towards the center)

Sample Questions 1) A horizontal force of 210 N is exerted on a 2.0 kg discus as it rotates uniformly in a horizontal circle at arms length or radius 0.90 m. What is the speed of the discus? 2) How large must the coefficient of static friction be between the tires and the road be if a car is to round a level curve of radius 85 m at a speed of 95 km/h?

Sample Questions 3) How fast (in rpm), must a centrifuge rotate if a particle 9.00 cm from the axis of rotation is to experience an acceleration of 115,000 g’s!? 4) In a “rotating ride of death”, people are ‘pinned’ to a wall in a circular room as the floor drops out. (clip) If the room has a radius of 4.6 m, and rotates at 0.50 rotations per second, what is the minimum coefficient of static friction needed so the people don’t slip down? (clip)

Video Clips of circular motion Cars in a circle Merry go around of death Minibike flip