Need help on physics question..keep getting it wrong. LINK INCLUDED

http://i48.tinypic.com/4l4x6t.png



really appreciate it.

Angular momentum = moment of inertia * angular velocity
moment of inertia = mass * radius^2
Since we are trying to determine the angular momentum of the system about their center of mass, the radius is the distance from the center of mass to each skater.

This is a teeter totter torque problem. The 57 kg skater is x meters from the center of mass, and 40 kg skater is (1 – x) meters from the center of mass.
57 * x = 40 * (1 – x) = 40 – 40 * x
97 * x = 40
x = 0.412 meter, 1 – 0.0.412 = 0.588 meter

The 57kg skater is 0.412 meters from the center of mass, and 40 kg skater is 0.588 meters from the center of mass.

For the 57 kg skater, I = 57 * 0.412^2
For the 40 kg skater, I = 40 * 0.588^2
Total moment of inertia = 57 * 0.412^2 + 40 * 0.588^2 = 23.505

Two ice skaters hold hands and rotate, making one revolution in 2.7 s
1 revolution = 2 * π radians
Angular velocity = 2 * π radians ÷ 2.7 s = 2.327 rad/s
Total angular momentum = 23.505 * 2.327 ≈ 54.7

Part B
Find the total kinetic energy of the system. Answer in units of J

Kinetic energy = ½ * I * ω^2 = ½ * 23.505 * 2.327^2 ≈ 63.64 J

I am still working

To find momentum and kinetic energy you will need both rotational inertia (I=mr^2) and angular velocity (w=radians/time). Also, you will need to find the center of mass.

The location of the center of mass is R=1/M(m1r1+m2r2), where R is the position of the center of mass and M is the total mass. If we take the 57kg mass to be m1 at the origin (r1=0) and the 40kg mass to be m2 at the other end 1 meter away (r2=1m) then the location of the center of mass is
R=(1/97kg)*(57kg*0m+40kg*1m)=40kgm/97kg… from the 57kg mass. This means that the 57 kg mass is 0.412 m from the center of mass and the 40kg mass is 0.588m from the center of mass.