Biophysics and machines

• How do you calculate the pressure exerted by something? (e.g. chocolate bar)

  Pressure = weight / area
• How do you calculate a weight of something in N?

  Weight = mass × gravity = 5 kg × 9.81 m/s²
• What is the pressure exerted by the suitcase on the ground when standing on its wide side?

  Pressure = weight / area
• What is the area of the suitcase when standing on its wide side (30cm by 20cm)?

  Area = 30cm × 20cm = 600cm²
• What is the pressure exerted by the suitcase when standing on its wide side?

  Pressure = $\frac{Weight}{Area} =$$\frac{49.05N}{600cm²}$
• What is the pressure exerted by the suitcase when on its end (20cm by 10cm)?

  Pressure = $\frac{Weight}{Area} =$$\frac{49.05N}{200cm²}$
• What is the pressure exerted by the suitcase when lying flat (30cm by 10cm)?

  Pressure = $\frac{Weight}{Area} =$$\frac{49.05N}{300cm²}$
• Which side of the suitcase exerts the most pressure on the ground?

  The side with the smallest area
• How could you determine which side puts the most pressure without calculations?

  By comparing the areas of each side
• What is the pressure exerted by the man on the roof when standing on both feet?

  Pressure = $\frac{Weight}{Area} =$$\frac{800N}{400cm²}$
• What is the pressure exerted by the ladder on the roof?

  Pressure = $\frac{Weight}{Area} =$$\frac{1200N}{5000cm²}$
• What is the pressure exerted by the excavator on the ground?

  Pressure = $\frac{Weight}{Area}$
• What are the learning objectives for the lesson on the Human Body and Levers?

  • State the function of the skeleton
  • Describe how muscles move bones
  • Give examples of levers, stating effort, load, and pivot
  • Explain advantages of using levers
• What are the learning objectives for the lesson on Moments?

  • Describe requirements for equilibrium
  • State the principle of moments
  • Describe the 'law of gravity' and its effects
• What are the learning objectives for the lesson on Centre of Gravity?

  • Explain how to find an object's centre of gravity
  • Explain how to keep an object in stable equilibrium
  • Describe effects when centre of gravity is above support point
• What are the learning objectives for the lesson on Pressure?

  • State and use the pressure equation
  • Explain pressure measurement in containers and pipes
  • Explain pressure effects on particles and depth changes
• What are the learning objectives for the lesson on Pressure in Gases?

  • Define pressure in gases
  • Explain factors affecting gas pressure
  • Explain why gas pressure increases with temperature
• What are the learning objectives for the lesson on Hydraulics?

  • Explain pressure transmission through liquids
  • Explain function of pressure in liquids
  • Explain hydraulic machine operation
• What are the learning objectives for the lesson on Pulleys?

  • Explain how pulleys reduce effort
• What are the key terms defined in the glossary?

  • Antagonistic: Muscle pairs pulling in opposite directions
  • Compression: Force applied while pushing
  • Contract: Muscle cells getting shorter
  • Effort: Force applied using machines
  • Equilibrium: Balanced forces with no net force
  • Fulcrum: Pivot point for turning
  • Gear: Wheel with teeth
  • Hydraulic: Pressure of moving liquids
  • Lever: Simple machine using turning effect
  • Load: Side of effort or load
  • Machine: Anything making work easier
  • Moment: Turning effect of a force
  • Muscle: Bundle of muscle fibres
  • Newton meter (N): Measure of turning effect
  • Piston: Device that pushes
  • Pressure: Force on a surface area
  • Pulley: Wheel with a groove
  • Rotation: Process of turning
  • Surface area: Average force on a surface
  • Tension: Muscle stretching
  • Torque: Area of pivot outside a gear
  • Turning force: Force with a turning effect