  When talking to secondary school students, first impressions are crucial.
Accidentally say something that sounds boring and you'll lose them in seconds.
A physical demonstration can be an eye-catching way to begin an activity or
spark off a conversation about mathematics. This is especially true in the
context of an event like a science fair where there are hundreds of other
exhibitors and stands, possibly involving loud music and/or dancing robots!
  In this article we describe three devices that were built to illustrate
specific physical phenomena that occur in the human body. Each device
corresponds to a simple mathematical model which contains both elements that
are accessible to pupils in the early years of secondary education and more
challenging mathematical concepts that might appeal to A-level students. Two of
the devices relate to the Windkessel effect, a physical phenomenon that
regulates blood flow, and the third demonstrates the elastic properties of
ligaments and tendons.
