physics: unit 4 - explaining motion

• newton's first law of motion

  an object in motion will remain in motion unless acted upon by another force
• newton's second law of motion

  the acceleration of an object is equal to the net force acting on the object divided by the object's mass (f=ma)
• newton's third law of motion

  when one object exerts a force on a second object, the second object exerts an equal force in the opposite direction on the first object
• forces in an interaction pair must...


  act on different objects, be equal in magnitude, be the same type of force, be opposite in direction
• force


  a push or pull exerted on an object due to interaction with another object
• weight (N) equation


  mass (kg) x gravitational field strength (N/kg)
• acceleration (m/s^2) equation


  change in velocity (m/s) / time (s)
• conservation of momentum


  momentum of a system remains constant when there are no net external forces acting on it
• in collisions


  total momentum before = total momentum after
• inertia


  the tendency of an object to resist a change in motion
• moment of a force

  the rotational effect of an object with a pivot due to the resultant force acting on it
• pivot


  a fixed point about which an object can turn
• equilibrium is when...


  sum of anticlockwise moments = sum of clockwise moments
• work done (J or Nm) equation

  force (N) x distance (m)
• gravitational potential energy (J) equation


  mass (kg) x gravitational field strength (N/kg) x height (m)
• kinetic energy (J) equation


  0.5 x mass (kg) x (speed(m/s))^2
• momentum (kgm/s) equation


  mass (kg) x velocity (m/s)
• force (N) equation


  mass (kg) x acceleration (m/s^2)
• average speed (m/s) equation


  distance (m) / time (s)
• constant acceleration is when...

  (final speed)^2 - (initial speed)^2 = 2 x acceleration (m/s^2) x distance (m)