1. Circular Motion = the movement of an object at constant speed around a circle with fixed radius Axis – straight line around which rotation takes place Rotation – object turns around an internal axis Ex. Ice skater Revolution – object turns around an external axis Ex. Earth around the sun

2. Rotational Speed Linear speed – distance/time Tangential speed – speed along a circular path Rotational speed – number of rotations per unit of time Example: Carousel horses travel at same rotational speed but different tangential speed

3. Linking tangential and rotational speed Tangential speed is radial distance times the rotational speed V = r ω

4. Centripetal Force Force that causes an object to follow a circular path Ex. Force holding occupants safely in a rotating carnival ride F net = mv 2 r

5. Centripetal Acceleration Always points toward the center of the circular motion. Period (T) = time needed for an object to make one complete revolution Distance traveled = circumference Circumference = 2πr = πd

6. Other formulas Centripetal Acceleration equals the velocity squared divided by the radius A c = v 2 /r The number of revolutions equals the distance traveled divided by the circumference Revolutions = distance/circumference

7. Sample problems If a wheel has a diameter of 0.51 m and the wheel travels for 15 m, how many revolutions will it make? What is the tension in a 3.2 m length of string that whirls a 1.5 kg mass at 2.1 m/s in a horizontal circle?