Physics-pressure and moments

• How is pressure defined?

  Force divided by area of contact
• What two factors does pressure depend on?

  Size of force and size of area
• What is the equation to find pressure?

  Pressure = force / area
• What does F represent in the pressure equation?

  Force or weight measured in N
• What does P represent in the pressure equation?

  Pressure measured in N/m²
• What does A represent in the pressure equation?

  Area of contact measured in m²
• How are pressure units determined?

  Based on the units used for area measurement
• What is the unit for pressure when area is in m²?

  N/m²
• What is the unit for pressure when area is in cm²?

  N/cm²
• What is 1 Pascal (Pa) equivalent to?

  1 N/m²
• How can you rearrange the pressure equation to find force?

  F = P x A
• How can you rearrange the pressure equation to find area?

  A = F / P
• Calculate the pressure exerted by a person weighing 450N on an area of 200 cm².

  2.25 N/cm²
• What is the pressure exerted by a brick weighing 10 N on an area of 20 cm²?

  0.5 N/cm²
• Calculate the pressure exerted by a 1000 N elephant on an area of 0.5 m².

  2000 N/m²
• If a woman exerts a pressure of 100 N/m² and weighs 500 N, what is the area of the floor she stands on?

  5 m²
• What is the weight of machinery exerting a pressure of 16,800 Pa on an area of 0.5 m x 0.8 m?

  6720 N
• What is the weight of a clock with a mass of 0.5 kg? (g = 10 N/kg)

  5 N
• If a clock exerts a pressure of 2000 Pa, what is the area of its base?

  0.0025 m²
• How does pressure change with increasing force for a fixed area?

  Pressure increases as force increases
• Calculate the pressure exerted by two boxes of equal area (50 cm²) with weights of 100 N each.

  2 N/cm²
• Why does a person wearing snowshoes not sink into the snow?

  Pressure is spread over a larger area
• Why does a sharp knife cut through cheese easily?

  It has a smaller area for pressure
• Why are large tyres better for tractors in mud?

  They spread weight over a larger area
• When is high pressure needed?

  When force is concentrated on a small area
• When is low pressure essential?

  When force is spread over a large area
• What steps are involved in calculating your pressure when standing on two feet?

  1. Draw around one shoe on graph paper.
  2. Count area of footprint in cm².
  3. Multiply by two for both feet.
  4. Weigh yourself in kg.
  5. Calculate weight using Weight = mass x 10.
  6. Calculate pressure using P = F/A.
• What is the relationship between weight and pressure in a concrete block experiment?

  • Pressure = Weight / Area
  • Adding blocks increases weight.
  • Pressure increases with more blocks.
• What is the smallest number of blocks that will damage a surface with a pressure limit of 45 N/m²?


  3 blocks
• What factors affect air pressure?

  Altitude and weather conditions
• What happens to air pressure in aircraft cabins?

  It is pressurized to be higher than outside
• Why is low air pressure dangerous at high altitudes?

  It makes breathing difficult
• What is the effect of low air pressure on the human body?

  It can lead to suffocation without protection
• How does air pressure behave in relation to high and low areas?

  Air moves from high pressure to low pressure
• What are the applications of pressure in everyday life?

  • High pressure: drawing pins, emergency hammers
  • Low pressure: caterpillar tracks, large feet of elephants
• What is the formula to calculate pressure?

  Pressure = force / area
• How is air pressure created?

  By air molecules crashing into surroundings
• What happens to air pressure as altitude increases?

  Air pressure decreases with higher altitude
• Why do aircraft cabins need to be pressurized?

  To ensure passengers can breathe at high altitudes
• What is the pressure inside the aircraft cabin during testing?

  9 N/cm² (13 psi)