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Physics, 22.06.2019 00:30
Comedians like to joke that the reason we havenââŹâ˘t been visited by intelligent life from elsewhere in the universe is that aliens have been monitoring earthââŹâ˘s broadcasts of intellectually embarrassing tv programs, like gilliganââŹâ˘s island, fear factor, the jersey shore, and the jerry springer showand so consider us far too primitive to merit a visit. letââŹâ˘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
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Physics, 22.06.2019 17:40
You throw a baseball directly upward at time =0 at an initial speed of 14.9 m/s. what is the maximum height the ball reaches above where it leaves your hand? ignore air resistance and take =9.80 m/s2.
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Physics, 22.06.2019 22:00
Which of these is the best way to manage a natural resource
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Physics, 22.06.2019 22:30
The drag force, fd, imposed by the surrounding air on a vehicle moving with velocity v is given by fd = cdaĎv 2/2 where cd is a constant called the drag coefficient, a is the projected frontal area of the vehicle, and Ď is the air density. an automobile is moving at v = 80 kilometers per hour with cd = 0.28, a = 2.3 m2, and Ď = 1.2 kg/m3.
Answers: 2
A radio signal from a gps satellite takes only about 0.067 seconds to reach a gps receiver. if the s...
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