Posted by **Amber** on Monday, April 23, 2012 at 12:38pm.

Two ice skaters hold hands and rotate, making one revolution in 7.6 s. Their masses are 15 kg and 50 kg, and they are separated by 4.6 m.

Find the angular momentum of the system

about their center of mass.

Answer in units of J · s

Find the total kinetic energy of the system.

Answer in units of J

- Physics. PLEASE HELP!! -
**Elena**, Monday, April 23, 2012 at 4:07pm
Distance between the skaters is d, frequency is n =1/7.6 s^-1

Location of the center of mass

of the second skater of mass m2 is

x1 = d •m2/(m1+m2),

x2 = d - x1,

Moment of inertia of the system is

I= I1 +I2 =

= m1•x1^2 + m2•x2^2.

Angular momentum is

L = I•ω= I•2•π•n.

KE = I• ω^2/2 = I•(2•π•n)^2/2.

Check your given data. It seems to me that the distance 4.6 m is too much if the “skaters hold hands”. Moreover, the mass m1 = 15 kg is improbable for skater (this is the mass of the child of three).

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