: Một quả cầu nhỏ bằng kim loại có khối lượng m = 1,6g, được treo vào điểm O bằng sợi dây không dãn. Tích điện cho quả cầu với điện tích q = 4.10-8 C. rồi đặt hệ trong một điện trường đều có đường sức thẳng đứng, hướng lên, có độ lớn 4.105V/m. Lấy g = 10 (m/s2 ). Tính lực căng của dây

Avoltage source vs = 10 v is in series with a resistor of 10 kohm. if the source transformation theorem is applied, what will the value of the current source be in ma ?

Around faucet handle is part of a(n) a. lever b. screw c. inclined plane d. wheel and axle

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