Forces and Energy

• Scalar quantity


  Only has a size (magnitude)
• Vector quantity


  Has both a size and direction
• Force


  A push or pull that acts on an object due to the interaction with another object
• What is a vector quantity?

  Something with a direction and magnitude.
• Contact force


  When objects are physically touching (e.g. friction, resistance, tension, normal contact force)
• Non-contact force


  When objects are physically separated (e.g. gravitational, electrostatic, magnetic)
• The forces are the same size
• The resultant force on an object is zero if the forces on it are balanced
• Weight


  The force acting on an object due to gravity
• Calibrated spring-balance (newton meter)


  Instrument used to measure the weight of an object
• Centre of mass


  The point through which the weight of an object can be considered to act
• Elastic deformation


  An object can go back to its original shape and size when deforming forces are removed
• Inelastic deformation


  An object does not go back to its original shape and size when deforming forces are removed
• Finding the spring constant from a force-tension graph


  Find the gradient of the straight line section
• Moment


  The turning effect of a force
• The sum of all the clockwise moments about a point equals the sum of all the anticlockwise moments about that point on a balanced object
• Lever


  Reduces the amount of force needed to create a particular sized moment by increasing the distance from the pivot
• A small gear drives a large gear


  The moment of the force is increased