A swimmer swims from the north end to the south end of a 50 m pool in 25.2 s and makes the return trip to the starting position in 28.7 s. What is the average velocity for the first half of the swim?
What is the average velocity for the second half of the swim?
What is the average velocity for the round trip?

What is the shortest period of time in which a bacterium could drift at a constant speed of
4.2 mm/s across a petri dish with a diameter of 9.3cm?

Marc and Ana walk with a velocity of 1.24 m/s eastward. If it takes them 9 min to walk to the store, how far have they walked?

Aman pushes on a trunk with a force of 250 newtons. the trunk does not move. how much positive work is done on the trunk? 0.0 j -250 j 250 j 125 j

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

6–43 a food department is kept at 2128c by a refrigerator in an environment at 308c. the total heat gain to the food department is estimated to be 3300 kj/h and the heat rejection in the condenser is 4800 kj/h. determine the power input to the compressor, in kw and the cop of the refrigerator.