Topic 15- Forces and matter mark schemes

• Why is there constant pressure on people? (1 mark)

  • because of pressure from the atmosphere
• How could a spring distortion experiment be made more accurate (2 marks) list 5

  1. use smaller millimetres divisions
  2. use fixed weight values
  3. add more weights to increase the range
  4. move ruler close to spring
  5. repeat and take average
• Why can a spring no longer be compressed at one point? (1 marks)

  • because the coils are pressed together/ fully compressed
• Why does atmospheric pressure decrease with height above sea level? (1 mark)

  • the atmosphere gets thinner/ fewer air particles as height above sea level increases
• what are two factors that would affect the pressure of the atmosphere on an airplane as it ascends? (2 marks )

  • density of atmosphere/ the air gets thinner
  • temp of atmosphere/ the air gets colder
  • height of airplane/ less air above the airplane
• explain why a boat floyd lower when there is a load (6 marks)

  PRESSURE

  • difference in pressure between top and bottom of boat
  • pressure at bottom atmosphere plus depth of water
  • pressure at top just atmosphere
  • UNLOADED BOAT
  • density of boat less than density of water
  • floating objects displace water
  • causing up thrust which is equal to weight of boat
  • BOAT WITH LOAD
  • weight/ density increase because of load
  • more upthrust
  • weight of water displaces is the upthrust and equal to weight of boat
• What two measurements should be made on a spring to determine the extension? (2 marks)

  • initial length
  • final length
• Explain why when pushing a drawing pin into wood it goes into the wood instead of your thumb(6marks)

  • top of thumb tack has a larger surface area
  • pointed end has very small surface area
  • although there is same force, larger pressure makes the tip go into wood
  • flat end does not damage the thumb
  • pressure= force/ area