dave kunst is the first person verified to have completely circled the entire earth on foot in 4 years. Let us assume he traveled in a perfect circle around the earth and the center of his circle is same as the center of the earth. If he traveled through a tunnel through the center of the earth penetrating to other side of earth at the same average speed, how much time would he have taken​

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.