A4

• angular displacement

  the angle through which something has rotated
• angular velocity


  the time rate at which something is rotating
• angular acceleration


  the rate of change of angular speed
• torque


  the product of the magnitude of the force and the perpendicular distance etween the line of action of the force and the axis of rotation
• translational equilibrium


  the net force of the body is zero
• rotational equilibrium


  the net torque on the body is zero
• moment of inertia


  the distribution of mass of an extended body about an axis of rotation
• angular momentum


  the product of mass, speed and orbit radius of a particle
• conservation of angular momentum

  when the net torque on a system is zero, the angular momentum is conserved
• angular impulse


  the change in angular momentum
• moment


  its turning effect about a point

  the product of the force and the perpendicular distance from the point of th eline of action of the force
• the principle of moments


  for a system of forces acting on an object to be in rotational equilibrium, the sum of the anti-clockwise moments about the same point
• couple


  a pair of equal sized forces that have different lines of action but which are parallel to each other and act in opposite directions, either side of the axis of rotation
• a couple produces no resultant force on an object
• there is no translation acceleration and the object remains in the same position in a couple
• newton's second law for rotational motion


  The resulting angular acceleration (α) of an object is directly proportional to the net torque (τ) on that object
• conservation of angular momentum

  the total angular momentum of a system is constant provided that no net external torque is acting on it
• bodies in rotational equilibrium have a resultant torque of zero
• unbalanced torque applied to an extended, rigid body will cause angular acceleration