A launcher is used to launch a dart with initial speed u from a table at an angle, as shown above. The dart exits the end of the launcher at a heighth above the floor and lands a horizontal distance D from the end of the launcher. A close-up view is included that shows the dart in the launcher immediately before being launched. Inside the launcher. the dart rests on a platform with negligible friction and a compressed spring is released to push the dart out of the launcher Assume air resistance is negligible. a) A student creates an incorrect diagram shown above of the forces exerted on the dart at an instant in time after it has been launched but before it reaches the floor. Indicate what aspect of the diagram is incorrect. Assume air resistance is negligible.

A6,600 kg train car moving at +2.0 m/s bumps into and locks together with one of mass 5,400kg moving at -3.0m/s. what is their final velocity? +0.50 m/s -1.0 m/s +2.5 m/s -0.25 m/s

Jackson is designing a new heater, and he wants to experiment with different thermally conductive materials. which of these materials would be useful in conducting heat?

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