P9 - Forces and their effects

• non contact forces: gravitaional,electrostatic and magnetic
• contact force: friction, tension, air resistance and normal reaction
• frictional force is the force that opposes motion between two surfaces in contact.
• tension is the pulling force exerted by one object on another when it is being pulled apart or stretched.
• gravitational force is the attraction between any objects with mass.
• the strength of gravity depends on the distance between the objects and their masses.
• electrostatic fields affect charge objects
• there is normal contact force when an object is on a surface
• upthrust is when an object is in a liquid
• overall force=resultant force
• What does the length of the arrow represent in a vector diagram?

  The size (magnitude) of the force
• Which direction does weight act?

  downwards
• Which direction does friction act?

  Opposing the direction of motion
• Which direction does the normal contact force act?

  Perpendicular to the surface
• How do you work out the

  resultant force if the forces are at

  right-angles to each other?

  use pythogoras
• lubrication helps remove unwanted energy transfers