Levers and Lever Systems

Levers, Axes and Planes of Movement

In this course, Dr Adam Brazil (University of Bath) explores axes and planes of movement. In the first lecture, we think about levers and lever systems, reviewing all three classes of lever. In the second and final lecture, we think about the six degrees of freedom in the physical world, looking at the three planes of movement and the three axes of rotation. Photo by Scott Broome on Unsplash.

Levers and Lever Systems

In this lecture, we think about levers and lever systems, focusing in particular on: (i) understanding the purpose of a lever system being to create movement about a turning point, or fulcrum, which is a joint in the body; (ii) the four key features of a lever system being the rigid structure, the fulcrum, the load force and the effort force; (iii) a first class lever system being one which has a fulcrum in the centre and a rigid structure either side, with opposing effort and load forces on each side; (iv) an example of a first class lever system in the body being raising the head using the spine; (v) a second class lever system being one where the load sits in between the fulcrum and the effort; (vi) an example of a second class lever system in the body being standing up onto toes from being flat footed; (vii) a third class lever system being one where the effort sits between the load and the fulcrum; (viii) an example of a third class lever system in the body being a bicep curl; (ix) the fact that the efficiency of a lever depends on the relative positions of the effort and load to the fulcrum; (x) using the placement of a hand when pushing open a door to illustrate how this relative position impacts efficiency; (xi) comparing the efficiencies of the second and third class lever system examples of standing onto toes with a bicep curl.