Chapter 16- Circular motion

• What is a radian?

  The angle subtended by a circular arc with length equal to the radius of the circle
• Define Centripetal force

  A resultant force that keeps a body moving with a constant speed in circular path and acts perpendicular to the direction of motion.
• Define centripetal acceleration

  The acceleration of any object travelling in a circular path at a constant speed which always acts towards the centre of the circle
• Define angular velocity

  The rate of change of angle for an object moving in a circular path
• Centripetal force acts perpendicular to the velocity therefore therefore it has no component in the direction of motion so no work is done resulting in a constant speed
• For objects with the same angular velocity, linear velocity at any instant is directly proportional to the radius
• Centripetal acceleration depends on the speed of the object and the radius of the circular path. The greater the speed or smaller the radius, the greater the acceleration
• To investigate circular motion, a bung is connected to a string with a mass on the other end and passes through a glass rod. A paper clip is added to the string below the glass rod as a marker. The glass rod is held and the bung swung in a horizontal circle. The suspended weight will remain stationary for as long as the force is provides is equal to the centripetal force.
• The greater the speed of an object following a circular path, the greater the centripetal force required in order to make it follow this path. Banked surfaces can be used to travel at greater speeds while in circular motion. Due to the angle of the body in motion, there is multiple components which sum to provide the centripetal force.
• A conical pendulum is a simple pendulum which rotates at a constant speed. The time of each rotation depends on the length of the string and the gravitational field strength.