A stone is projected vertically upward with a velocity of 20 metre per second. 2 seconds later a second stone to is similarly projected with the same velocity when the two stones meet the second one is rising at a velocity of 10 metre per second neglecting air resistance calculate the length of time the second stone is in motion before they meet to velocity of the first Stone when they meet take g equals to 10 metre per second

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.