Apulley with radius r and rotational inertia i is free to rotate on a horizontal fixed axis through its center. a string passes over the pulley. a block of mass m1 is attached to one end and a block of mass m2, is attached to the other. at one time the block with mass m1 is moving downward with speed v. if the string does not slip on the pulley, the magnitude of the total angular momentum, about the pulley center, of the blocks and pulley, considered as a system, is given by:
a. (m1 – m2)vr + iv/rb. (m1 + m2)vr + iv/rc. (m1 – m2)vr – iv/rd. (m1 + m2)vr – iv/re. none of the above

Uranium has two naturally occurring isotopes. 238u has a natural abundance of 99.3% and 235u has an abundance of 0.7%. it is the rarer 235u that is needed for nuclear reactors. the isotopes are separated by forming uranium hexafluoride uf6, which is a gas, then allowing it to diffuse through a series of porous membranes. 235uf6 has a slightly larger rms speed than 238uf6 and diffuses slightly faster. many repetitions of this procedure gradually separate the two isotopes. what is the ratio of the rms speed of 235uf6 to that of 238uf6? express your answer to five significant figures.