Question

15. The factor most directly respon ho factor most directly responsible for making a black hole invisible is its a. size b. mass C. Color d. surface escape velocity hen you step on a weighing scale at noon Earth pulls you down and the overhead Sun pulls you upward. The reason the Sun's pull does NOT decrease your weight at noon is that a. you, the scale, and Earth are in freefall around the Sun b. the Sun's pull on you is negligibly small C. the Sun's pull is canceled by the gravitation of other celestial bodies d. the weighing scale is calibrated only in Earth weight 17. Suppose the Moon had twice as much mass as it now does and still orbited the Earth at the same distance as it does now. In this scenario, the ocean bulges on Earth would be a. larger b. smaller c. unequal in size d. negligibly different 18. Tidal forces in general are the result of a. the inverse-square law b. two or more sources of gravitation c. unequal forces acting on different parts of a body d. a combination of any kind of forces acting on a body 19. Suppose the Moon had twice the diameter but the same mass and same orbital distance from Earth. In that case, the high tides on Earth would be a. higher b. lower c. unequal in size d. practically the same

Answer 1

(15. Answer is (d) surface escape velocity The surface gravity of black hole is so high that object with the highest speed (speed of light) can not escape from its surface. Light cannot escape from the black hole, so we can't See ito Black holes are invisible because they are so dense. They have very high density and their gravity is so strong that not even light can escape. a

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