RP: The Young Modulus

• What is the aim of the Young Modulus experiment?

  To measure the Young Modulus of a metal wire

  
• What is the independent variable in the Young Modulus experiment?

  Force (or load) (N)

  
• What is the dependent variable in the Young Modulus experiment?

  Extension (m)

  
• What are the control variables in the Young Modulus experiment?

  • Original length of wire
  • Thickness of the wire
  • Metal used for the wire
• What is the resolution of a metre ruler?

  1 mm
• What is the resolution of a micrometer?

  0.001 mm
• What is the method for measuring the Young Modulus of a copper wire?

  1. Measure diameter with micrometer.
  2. Set up apparatus with taut wire.
  3. Measure original length and mark reference.
  4. Record initial reading.
  5. Add 100 g mass and record new reading.
  6. Repeat with additional 100 g masses.
• What is the equation for the Young Modulus?

  Young Modulus = $\frac{F \cdot L}{A \cdot \Delta L}$

  
• What does the variable F represent in the Young Modulus equation?

  Force (or load) (N)

  
• What does the variable L represent in the Young Modulus equation?

  Original length of the wire (m)

  
• What does the variable A represent in the Young Modulus equation?

  Cross-sectional area of the wire (m²)

  
• What does the variable $\Delta L$ represent in the Young Modulus equation?


  Extension (m)

  
• How is the cross-sectional area of the wire calculated?

  Area = $\frac{\pi d^2}{4}$

  
• How do you find the load in the Young Modulus experiment?

  Multiply each mass by $g (9.81 \text{ N/kg})$
• What is the gradient of the force-extension graph?

  Gradient = $\frac{F}{\Delta L}$
• How do you calculate the Young Modulus from the gradient?

  Multiply gradient by $\frac{L}{A}$

  
• What are the systematic errors in the Young Modulus experiment?

  • Use a vernier scale for precision
  • Wire may deform if extended past elastic limit
  • Check wire returns to original length
• What are the random errors in the Young Modulus experiment?

  • Parallax error from ruler reading
  • Repeat experiment for average extension
  • Measure diameter in several places for average
• What safety considerations should be taken during the experiment?

  • Wear safety goggles
  • Cushion below mass hanger
• What should be done to improve the reliability of the Young Modulus experiment?

  Repeat readings and use longer wire
• What is the value of g used in the experiment?

  $9.81 \text{ N/kg}$
• What is the relationship between force and extension in the Young Modulus experiment?

  Directly proportional until elastic limit