Force In Balance (P8)

• scalar quantity

  only has magnitude, no direction
• vector quantity

  has both magnitude and direction
• Unit of force

  N (Newton)
• Contact forces

  Objects have to be touching
• non-contact force

  Objects don't need to touching
• Examples of contact forces

  friction, air resistance, tension and normal contact force
• Examples of non-contact forces

  gravitational forces, electrostatic forces, magnetic forces
• Newton's third law

  Two interacting objects ever equal and opposite forces on each other
• Resultant force

  a single force that has the same effect as all the forces acting on the object.
• Newton's first law

  If zero resultant force acts on stationary object, object doesn't move

  If zero resultant force acts on moving object, it continues moving at the same velocity

  If non-zero resultant force acts on an object, object accelerates
• Newton's Second Law

  Resultant force = mass x acceleration
• Moment

  The turning effect of a force
• Moment equation

  Moment (Nm) = force (N) x distance from pivot (m)
• Levers

  Make it easier to do work
• Describe how levers act as force multipliers.

  They allow a larger force to act upon the load than is supplied by the effort
• Gear

  Used to transmit the rotational effect of a force from one place to another

  Larger gears cause bigger moments but turn more slowly
• Explain how gears can give a bigger turning effect.

  The smaller wheel turns more quickly but with less force, while the bigger one turns more slowly with more force.
• Centre of mass

  Point at which an object weight appears to act
• Displacement

  Distance in a given direction
• Load

  the weight of an object raised by a device used to lift the object, or the force applied by a device when it is used to shift an object.
• magnitude

  the size or amount of a physical quantity
• Parallelogram of forces

  a geometrical method used to find the resultant of two forces that do that do not act along the same line.
• Principle of moments

  for an object in equilibrium, the sum of all the clockwise moments about any point = the sum of all the anti-clockwise moments about that point
• Equilibrium

  a state in which opposing forces or influences are balanced.