PowerPoint

Conservations of M om

entum

and Energy

U nit III A

ssignm ent

C overed concept:

angular m om

entum conservation

from m

ovie “Ice P rincess”

L=Iw =constant

I : m om

ent of inertia w

: rotational velocity

(Conservation of angular m om

entum , n.d.)

O bserved

: C asey spins slow

er w hen her arm

s are extended and faster w

hen her arm s are draw

n in.

E xplanation

: I≈ m r 2

m : m

ass of her arm r: distance from

the rotation axis

I is proportional to the square of r. I is greater as the length of arm

increases. T he spinning speed w

decreases as the length of arm

increases and vice versa. T hat is, this phenom

ena can be explained by the angular m

om entum

conservation; L=Iw =const.

A ssum

e: the shape of C asey is a solid cylinder w

ith 50 kg Æ

I=1/2 m r 2= 1 [kg m

2] w hen r= 0.2 m

eter. w

=1revolution/second=1x 2π radian/second

L=Iw =2π

kg m 2/s

References