forces and motion

• what is a contact force

  when objects physically touch
• what is a non contact force

  when not touching - magnetism, electrostatic and gravity
• what is a scalar

  a quantity that only has magnitude
• what is a vector

  • quantity with magnitude and direction
  • measures force
• what is a resultant force

  • by adding the forces acting on a direction
  • label which side
  • if at right angles make a triangle and use Pythagoras
• examples of scalar quantities

  • distance
  • speed
  • mass
  • energy
  • temperature
• examples of vector quantities

  • displacement
  • velocity
  • acceleration
  • force
  • momentum
• what is weight

  • the force that gravity pulls an object down with
  • mass x gravitational field strength
  • earths weight is 9.8 N/KG
• what does work done mean

  energy transferred by a force
• what is hookes law

  • force and extension are directly proportions
  • force (N) = spring constant (M/m) x extension
  • any object that deforms elastically obeys
• spring practical aim

  to determine the spring constant/stiffness for a spring
• spring practical variables

  independent - force

  dependent - extension
• spring practical steps

  1. fix top of a spring to a clamp on a retort stand
  2. fix a ruler next to it with zero mark lined up with the bottom of the spring
  3. for accurate measurements, make sure ruler is as close to spring as possible and get on eye level to reduce parallax error
  4. add slotted masses on a hanger to the spring to change the force/tension
  5. calculate force from weight - f= mass x gfs
  6. plot force against extension
• how is speed or velocity calculated

  distance or displacement/time
• acceleration

  change in velocity/time
• newtons first law

  if no resultant force acts on an object its motion is constant
• what is inertia

  the tendency for an objects motion to stay constant if there is no force
• newtons second law

  • force = mass x acceleration
• aim of newtons second law practical

  verify newtons second law
• variables of newtons second law practical

  independent - force

  dependent - acceleration

  control - mass, trolley
• newtons second law practical steps

  1. attach slotted masses to a trolley on a track or glider on an air track so they hang over a pulley
  2. let trolley move with weight of masses
  3. its flag will pass through 2 light/photogates connected to a datalogger which calculate acceleration
  4. change the force by removing masses from the hanger and placing them on the trolley
  5. this is crucial as the total mass being accelerated must remain constant
  6. plot force against acceleration, which should show a directly proportional relationship
• newtons 3rd law

  for every action there is an equal and opposite reaction
• what is thinking distance effected by

  • speed
  • distractions
  • alcohol
  • drugs
  • tiredness
• what is braking distance effected by

  • speed
  • condition of brakes, tyres, road
  • weather conditions
• momentum

  • mass x velocity
  • in any collision total momentum is always conserved