Contact and Non-Contact Forces

• Forces


  Either contact or non-contact and involve lots of interaction
• Vectors


  • Have magnitude and direction
• Vector quantities


  • Force
  • Velocity
  • Displacement
  • Acceleration
  • Momentum
• Scalar quantities


  Have only magnitude and no direction
• Scalar quantities


  • Speed
  • Distance
  • Mass
  • Temperature
  • Time
• Vectors


  Usually represented by an arrow, length shows magnitude, direction shows direction
• Velocity and speed


  Velocity is a vector, speed is a scalar quantity
• Both bikes are travelling at the same speed, v (the length of each arrow is the same), but have different velocities because they are travelling in different directions
• Contact forces


  Require two objects to be touching for the force to act
• Non-contact forces


  Do not require the objects to be touching for the force to act
• When two objects interact, there is a force produced on both objects
• Interaction pair


  A pair of forces that are equal and opposite and act on two interacting objects
• Interaction pair


  • The Sun and the Earth are attracted to each other by the gravitational force
  • A chair exerts a force on the ground, whilst the ground pushes back at the chair with the same force (the normal contact force)