Question

The divers leave the springboard with their arms and legs stretched out and then pull them inwards to exhibit somersaults. why ?

Answer 1

Have you heard of something called as "moment of inertia".. and a beautiful and a mind blowing concept of rotational physics called as "conservation of angular momentum"? if not.. you need to study that first.. to completely understand in dept the mechanism of this behavior !... and if you have a good understanding of it.. then you have enough clues already :P.. so do reply ;-)!

Answer 2

Yeah, I know it deals with moment of inertia. But what actually happens here ?

Answer 3

ok.. i ll give you a video.. in that i have explained examples.. in that i have included the diver board example.. wait!

Answer 4

http://www.youtube.com/watch?v=J14NnWLaFWI

Answer 5

So, when the surface area decreases, the moment of inertia increases.

Answer 6

its the radius that matters..

Answer 7

and if radius decreases moment of inertia decreases.. and hence angular velocity goes up.. so more sommersaults!

Answer 8

Oh, so now I get it. Thank you.

Answer 9

But why do they stretch their arms at first ?

Answer 10

see..

\[I \omega = constant\].. if no net force is present.. hence once you start your motion.. that product will remain a constant when you are in air..

so you initially stretch your arms and legs.. such that you have a big I (moment of inertia).. and you can even jump higher.. and you ll have some value of w..

now once you are air borne you coil yourself .. so you decrease I.. and hence your w.. goes up! .. so you initially stretch as to give yourself a big moment of inerita!

Answer 11

Wow, I never knew there were such concepts behind this. Thank you so much.

Answer 12

your welcome :)