Which claim about the universality of gravity is not supported by evidence? A. Any two objects that have mass also have a force of gravity acting between them, no matter how far apart they are.

B. The gravitational force between two objects depends only on their masses.

C. The gravitational force between two objects increases if mass is added to one object.

D. The gravitational force between two objects increases if the objects move closer together.

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.