Circular Motion Or I go right round baby right round like a record baby right, right, right, round?

Two Types of Spin Rotation Spin about axis that is inside of an object Object is rigid meaning there are physical connections between parts Examples: Earth about N-S axis, basketball spinning on finger, flipping person or car, tire turning Revolution Spin about axis that is outside of object Objects have no physical connections to parts Examples: car rounding curve, Earth’s orbit around sun, people running around track.

Two Types of Speed Tangential Speed Tangential Speed = distance / time Units of m/s, km/hr, ft/s Direction is tangent to curve object is following (inertial path In a rotation the tangential speed is lowest near the axis and greatest furthest away from the axis Tangent velocity = radius x angular velocity Angular Speed Angular speed = # spins / time Units of radians/second, degrees/ second and rpms Direction uses right hand rule In a rotation the angular speed is the same no matter where you are on the object

Inward or Centripetal Net Force A net inward (centripetal) force is required on an object moving in a curved or circular path. The inward force does NOT change the speed of the object moving in the curved or circular path, but it does change its direction. Required Inward force – Directly related to tangential velocity squared and mass of object. Inversely related to radius of curvature. – Required inward force = mass x (tangential velocity) 2 / radius of curvature = mv 2 /r Inward net force can be one of many forces (tension, gravity, normal force) or the sum of several forces.

Centrifugal Farce Centrifugal force would be an outward or center fleeing force. Alleged Examples – Sliding in back seat of car during turn – Bug in whirling can – Test Tube in Centifuge? – Amusement park ride w/no floor In all these examples an object’s inertia accounts for the motion. Only force is inward centripetal net force. Centrifugal Force

Artificial Gravity In rotating space station astronauts would be thrown to outside wall of station making residents feel floor like they do in gravitational field. Faster rotation results in an increase in this “gravity’ “Gravity” will also vary with where you are on station. – Center=> no motion=> 0 gravity – Outside Edge=> fastest rotation=>1 g