topic 9 - forces and their effects

• what is a force?

  a push or pull acting on an object due to an interaction with another object
• what are two categories forces can be split into?

  • contact forces
  • non - contact forces
• 3 examples of contact forces:

  • friction
  • air resistance
  • tension
• 3 examples of non contact forces:

  • gravitational forces
  • electrostatic forces
  • magnetic forces
• if force a vector or scalar, why?

  • vector
  • has both magnitude and direction
• what is a scalar quantity?

  • a quantity that has only magnitude
  • is not dependent on direction
• what is a vector quantity?

  • quantity that has both magnitude and direction
• 3 examples of vector quantities

  • velocity
  • displacement
  • force
• examples of scalar quantities:

  • temperature
  • time
  • mass
  • speed
  • distance
  • energy
• what is an alternative name for the turning effect of a force?

  • a moment
• state the equation used to calculate the moment of a force

  moment of a force (nm) = force(N) x distance(m)
• what distance measurement is used when calculating a moment?

  • the perpendicular distance from the pivot to the line of action of the force
• if an object is in equilibrium what can be said about the moments acting on the object?

  • the clockwise moments are equal to the anti clockwise moments
• how do levers make use of moments?

  • increase the perpendicular force from the pivot
  • decrease the force needed to produce the same moment
• how does lubricating levers/gears improve efficiency?

  • less resistance; less energy is dissipated/wasted (as heat) overcoming frictional forces