We are living in uncertain times and as students and families are stuck at home during this pandemic we thought it would be fun to demonstrate some basic biomechanical principles in action using commonplace items that are found around the home, to provide an understanding of the diversity of body form and how it may relate to function.
Materials needed for Activity 1:
• 10 litre bucket with handle, nearly filled with water
• Alternatively, something suitably heavy (> 5 kg) with a handle, e.g., fully laden backpack, kettle bell.
What to do:
• Place the bucket on the ground at your feet.
• Test 1: using both hands, lift the bucket up to chest height and close to the chest.
• Test 2: now lift the bucket gain, but this time do it at arm’s length.
What does this illustrate?
• Notice how lifting the bucket at arm’s length was more difficult to do (i.e., required more muscular effort)?
• The only thing in the system that changed between the two tests was the distance that the bucket was from the pivot (mainly the shoulder joint). By having the mass located further away from the pivot, this requires a larger turning force (or ‘moment’) to do the same amount of work.
• Yet the amount of moment that the shoulder muscles can exert for a given amount of effort hasn’t changed.
• Therefore, the muscles must work harder to provide the additional moment needed to lift the bucket up.
• This activity illustrates the concept of ‘mechanical advantage.’
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