In a stage production of peter pan, the 63 kg actress playing peter has to fly in vertically, and to be in time with the music, she must be lowered, starting from rest, a distance of 2.6 m in 2.2 s. backstage, a smooth surface
sloped at 58◦ supports a counterweight of mass m. what is the mass of the counterweight that must be used? the pulley is of negligible mass
and is frictionless. the acceleration of gravity is 9.81 m/s^2.
answer in units of kg.

Discuss how the hardness or softness of the landing surface is related to the time required to stop the egg

Scientific models are based on current knowledge, which can limit their effectiveness when new discoveries are made.

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.