ApEng

• What is the definition of a light object in physics?

  Weightless
• How is a particle defined in physics?

  Object considered as point
• What does a smooth surface imply in physics?

  No friction
• What does a rough surface imply in physics?

  Presence of friction
• What factors determine the effect of a force?

  Magnitude, direction, point of application
• What unit is used to measure force?

  Newton (N)
• What is a reaction force?

  Acts on body in contact with another
• What does frictional force do?

  Opposes movement over rough surfaces
• What is gravitational pull also known as?

  Weight
• What is tension in physics?

  Attachment to another body
• How is the resultant vector calculated?

  R = a + b + c + d + …
• What is the special case for component vectors?

  They are perpendicular or inclined at an angle
• How is the magnitude of R calculated for perpendicular vectors?

  Using Pythagoras theorem
• How is the magnitude of R calculated for vectors inclined at an angle?

  Using cosine rule
• How is the direction of R determined for inclined vectors?

  Using sine rule
• What does resolving vectors involve?

  Finding components of a vector
• How are Cartesian vectors expressed?

  Using symbols i and j
• What does the symbol i represent in Cartesian vectors?

  Vector of magnitude one unit in direction Ox
• What does the symbol j represent in Cartesian vectors?

  Vector of magnitude one unit in direction Oy
• How can vector F be expressed in Cartesian notation?

  Using components parallel to Ox and Oy
• What is the condition for a body to be in equilibrium?

  Resultant force R=0
• What does zero resultant force indicate?

  Does not necessarily mean equilibrium
• What are the equilibrium conditions?

  R=0, no turning effect, velocity unchanged
• What are concurrent forces?

  Forces acting on a single point
• What is the condition for concurrent forces?

  R=0, sum of components is zero
• What must be true for forces in equilibrium in Cartesian notation?

  Sum of i and j components must be zero
• What must two forces in equilibrium be?

  Equal and opposite, same straight line
• What must three forces in the same plane do to be in equilibrium?

  Lines of action must pass through one point
• What is the triangle of forces method?

  Represents forces by three sides of a triangle
• When is Lami’s theorem used?

  When angles between forces are known

  
• What does Lami’s theorem state?

  Forces must be proportional to sine of angles

  
• What is the condition for three non-parallel forces in equilibrium?


  They must be concurrent
• What is friction in physics?

  Opposes movement between two surfaces
• When does friction exist?

  When one body tends to slide over another
• How does friction behave as the tendency to move increases?

  Friction increases
• What happens when the limiting value of friction is reached?

  Frictional force can't increase further
• What is the unit of moment of a force?

  Newton meter (Nm)
• How is the moment of a force calculated?

  Moment = force x distance from O
• What defines the direction of moments?

  Anticlockwise = positive, clockwise = negative
• What happens when a force passes through the axis of rotation?

  Distance d from axis is 0