Two ice skaters, of mass 30 kg and 80 kg, are skating across the surface of a frozen lake on a
collision course, with respective velocities of 2.0 m/s in a general north direction, and 1.0 m/s
generally west, as shown above. After they collide, the pair of skaters move off in a direction
north of west with a momentum of approximately 100 kg m/s. How much kinetic energy was
lost in the collision?
OJ
110)
55
70)
120

Which is not a source of noise pollution? a)airplanes b)acid rain c)machines d)cars

An asteroid is discovered in a nearly circular orbit around the sun, with an orbital radius that is 2.47 times earth's. what is the asteroid's orbital period, its "year," in terms of earth years?

Comedians like to joke that the reason we haven’t been visited by intelligent life from elsewhere in the universe is that aliens have been monitoring earth’s broadcasts of intellectually embarrassing tv programs, like gilligan’s island, fear factor, the jersey shore, and the jerry springer showand so consider us far too primitive to merit a visit. let’s check the assertion that aliens could have been receiving them. tv programs are broadcast at a frequency of about 100mhz with about 100kw of total power in 30frames per second, which emanatesroughly uniformly in all directions. assume that interstellar space transmits these broadcasts without attenuation. no matter how smart they are, aliens would require at least one photon per frame to interpret our signals. findthe number of photons per unit time per unit area reaching a receiver on a possible planet in the nearest star system, which is about 4 light-years away (a light-year is the distance light travels in a year). if aliens aimed a receiver or detector directly at earth, how big (in diameter) would it have to be to receive a photon per frame