agine slicing a thick disk of radius R in half along its diameter. If you stand the half-disk on its curved edge and nudge it, it will rock back and forth. If the rocking is not too extreme, the time T required for a complete back-and-forth oscillation turns out to be nearly independent of the angle through which the disk rocks. The only other things that T might plausibly depend on are the disk's radius R, its mass M, and the local gravitational field strength g (in m/s2), since gravity is what is causing the rocking motion. (If you think about it, the disk's thickness is only relevant in that a thicker disk has more mass than a thinner one, so we already have this covered if we consider dependence on M.) Use dimensional analysis to find a reasonable formula for this rocking time up to a unitless constant.

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

Which safety measures should you follow during a thunderstorm? check all that apply. (a) avoid touching anything that conducts electricity. (b) avoid touching a person who has been struck by lightning. (c) go outside. (d) keep your computer turned off. (e) stay out of water. (f) stay inside.

Astudent pushes on a 20.0 kg box with a force of 50 n at an angle of 30° below the horizontal. the box accelerates at a rate of 0.5 m/s2 across a horizontal floor. what is the value of the normal force on the box? 200 n 243 n 156 n 225 n