4X01: Kinesiology

1
4X01 Kinesiology

• Moment of Inertia

2
Learning Outcomes

• By the end of this presentation you should be
  able to
• Explain the concept of moment of inertia
• Outline the influence of moment of inertia on
  sport and exercise movements

3
Moment of Inertia

• Moment of inertia is the reluctance of an object
  to change its rotational state of motion.
• Moment of Inertia is dependant on the mass of an
  object and how that mass is distributed relative
  to the axis of rotation
• ISmiri2

4
Moment of Inertia
5
Radius of Gyration

• To help visualise the concept of moment of
  inertia sometimes the idea of a radius of
  gyration is used. The is the idea that the mass
  of an object can be visualised as being located
  in an imaginary ring about the axis of rotation

6
Radius of Gyration
7
Demonstration using turntable
8
Principles

• Distributing mass away from the axis of rotation
  increases the moment of inertia.
• Distributing the mass close to the axis of
  rotation reduces the moment of inertia.

9
Examples in Sport

• Ice skating
• Somersaults in gymnastics
• Twisting in diving
• Questions
• A sprinter is often told to flex their knee more
  during the swing phase in order to enable them to
  bring their leg through faster. Why?
• Why does a gymnasts ability often decrease as
  they grow larger?