Testing the length and strength of beams

Testing the length and strength of beams

ZIMSEC O Level Combined Science Notes: Experiment:To investigate whether the depth of a beam affects its strength

Aim: To show how the length of a beam affects its strength

Materials: drinking straws, clamps, weights


  1. Clamp the ends of a straw and measure its length
  2. Add weights in the middle of the straw and find its breaking strength
  3. Shorten the straw by 2 cm a time and find the breaking strength of each length length
  4. Put the results in a table and plot them on a graph
  5. Repeat steps 1 to 3 using four or five straws tied together

Results and Observations

  • The longest beam is much more easily broken
  • The longer the beam the more easily it can be broken
  • This problem can be solved by having multiple support points along the length of the beam
  • When more straws are used the beam becomes stronger and supports more mass/weights


  • The strength of a beam decreases as its length increases
  • Multiple support points can be used to reduce the impact of this effect
  • A beam is stronger when it is made thicker

To access more topics go to the Combined Science Notes page.