If 6 J of work is needed to stretch a spring 10 from 10 cm to 12 cm and another 10 J is needed to stretch it from 12 cm to 14 cm. What is the natural length of the spring?

What is the average speed of a car that travels 40 mph for 1 hour and 60 mph in another hour?

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.

Aspring that is stretched 2.6 cm stores a potential energy of 0.053 j. what is the spring constant of this spring?