forces

• is force a vector or scalar quantity

  force is a vector - it has size and direction.
• what unit is force measured in?

  newtons, N
• state newtons first law

  in the absence of unbalanced forces, a body will remain at rest, or if moving, continue to move in a straight line at a constant velocity.
• how will you use newtons first law in questions?

  if an object is moving with a constant velocity (or at rest), the forces are balanced
• state newtons second law (in words)

  the acceleration of an object is inversely proportional to its mass, directly proportional to the resultant force on it and takes place in the same direction as the resultant force
• state newtons 2nd law (mathematically)


  F = ma
• what do each letter represent in F = ma?

  F = resultant force (N)

  m = mass (kg)

  a = acceleration (m/s²)
• what do we mean by resultant force?

  the overall effect on an object
• state newtons 3rd law

  every action force has an equal and opposite reaction force
• what is friction?


  friction is the force that opposes motion
• what is the definition of mass?

  mass is the amount of matter in an object
• what is mass measured in?

  kilogram, kg
• what is the definition of weight?


  weight is a force due to the pull of gravity on the object
• what is weight measured in?

  newtons, N
• what is the value of the pull of gravity on earth?

  10 N/kg
• equation used for weight

  W = mg
• what do each letter mean

  W = weight (N)

  m = mass (kg)

  g = gravity (10N/kg)
• in the absence of air resistance, what is true about any falling object?


  all objects in the absence of air resistance fall at the same rate regardless of their mass
• if an object was allowed to fall freely from rest what will its acceleration be?


  10 m/s²
• if an object is fired vertically upwards, what will its retardation be?


  10 m/s²