1 - Pressure and Moments

• Pressure


  A measure of the force exerted per unit area on an object, calculated by dividing force by area (Pressure = Force / Area)
• Moment


  A measure of the turning effect of a force about a pivot or axis, calculated by multiplying force by distance (Moment = Force x Distance)
• What are moments measured in?

  Newton metres

  Newton centimetres
• What does a lever do?


  Multiplies the force (by using a large distance), to make a job easier
• What is the principle of moments?


  The clockwise and anticlockwise moments are equal in equilibrium.
• What does pressure measure?

  Force per unit area
• What is the formula for pressure?

  Pressure = force ÷ area
• What are the units of pressure?

  N/m² or N/cm²
• What is the unit of pressure called?

  Pascal, Pa
• If the weight is 450N and the area is 394 cm², what is the pressure?

  $1.1 \text{ N/cm}^2$
• What happens to pressure when force is spread out over a larger area?

  Pressure is reduced
• What happens to pressure when force is concentrated on a smaller area?

  Pressure is increased
• What is the relationship between pressure and depth in a fluid?

  Greater depth means greater pressure
• What causes increased pressure at greater depths in water?

  More weight of water above
• What factors affect pressure in a fluid?

  Depth, weight, strength of gravity, mass, density
• What is the formula for calculating pressure in a fluid?

  Pressure = height × density × gravity
• How do adjacent cogs in gears move?

  They turn in opposite directions
• What happens when a cog with fewer teeth turns?

  It rotates quicker
• If a 6-tooth cog turns twice, how many turns does a 10-tooth cog make?

  0.86 turns
• What are hydraulics used for?

  They are force multipliers
• What is true about pressure in a hydraulic system?

  Pressure is the same at both ends
• What is a characteristic of liquids in hydraulic systems?

  They do not compress like gases
• If the pressure is 2 N/m², what is the force if the area is 5 m²?

  $F =$$P \times A =$$2 \text{ N/m}^2 \times 5 \text{ m}^2 =$$10 \text{ N}$