Physics Help Forum Moment of inertia of a human body

 Kinematics and Dynamics Kinematics and Dynamics Physics Help Forum

 Jul 12th 2017, 06:14 AM #1 Member   Join Date: Jan 2015 Posts: 94 Moment of inertia of a human body Hi everyone, I have come across a problem and I just don't know how to start to tackle it. The problem is as follows :- Estimate your own moment of inertia about a vertical axis through the centre of the top of your head when you are standing up straight with your arms outstretched. Make reasonable approximations and measure or estimate the necessary quantities. Firstly I am uncertain as how to decide what shape of figure I am dealing with (is the body described in the question above to be considered a hollow sphere , a solid sphere, a slender rod or a combination of these ? Or something else?) I just cannot work out the initial figure or combination of figures I am working with and so I am at a loss as to which equation for moment of inertia I should be using. Also is it one or more directions for the axis of rotation involved (one for the body and another for the outstretched arms ?) Can anybody help me start this problem ? Jackthehat
 Jul 12th 2017, 06:23 AM #2 Senior Member   Join Date: Aug 2010 Posts: 272 Are you shaped like a sphere? I can't speak for your body but would treat mine as a cylinder (the main trunk of the body) with two smaller cylinders (the arms) extending from the axis of the first cylinder. The axis of rotation is given as "a vertical axis through the centre of the top of your head."

 Tags body, human, inertia, moment