Which point refers to the epicenter of an earthquake?
a.
an underground point where an earthquake starts
b.
a point on the surface directly above the hypocenter of the earthquake
c.
a point on the surface that cracks first
d.
a point on the surface that shakes first

Arunner is training for an upcoming marathon by running around a 100-m-diameter circular track at constant speed. let a coordinate system have its origin at the center of the circle with the x-axis pointing east and the y-axis north. the runner starts at (x, y) = (50 m, 0 m) and runs 2.5 times around the track in a clockwise direction.

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.

Jaylen is a championship runner of the school's track team. during one of his trials, his speed was measured at 15.1 m/s. find jaylen's kinetic energy during that trial if his mass is 54.6 kg.