1. The problem statement, all variables and given/known data small block (mass .025 kg) on frictionless horizontal surface is attached to massless cord passing through a hole in the surface. Block is revolving around the hole in the center, with initial angular speed w1 = 1.75 rad/s, 0.3 m away from the hole. The chord is pulled from below, shortening the radius of the circle to 0.15m. Treat block as a particle. >is angular momentum conserved? >what is new angular speed? >what is change in kinetic energy of block? >what is the work done by pulling the chord? 2. Relevant equations k = (1/2)mv^2 + (1/2)Iw^2 v = rw I = mr^2 3. The attempt at a solution I'm not sure if angular momentum is conserved. I want to say no because it doesn't seem that the sum of the external force, in this case the tension in the string, sums to zero.. But then the equation becomes K1 + Work(other) = K2. Work is W = F*dr.... but how do I solve for F? F = ma(x).... but in this case the tension in the rope is antiparallel to the radial acceleration.... a(rad) = (w^2)r. or does the force from the tension in the rope equal ma(tangtial) which is perpendicular to the force vector... where a(tan) = r*angular_accel. Im a little confused. Thanks for any help.