Which of the following statements about black holes is false. a. astronomers have never seen a black hole. b. a black hole sucks in matter like a vacuum cleaner. c. no light can escape from a black hole. d. all of the mass in a black hole is concentrated in a single point.

What challenges did you encounter during the circuit training program?

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Consider an ordinary, helium-filled party balloon with a volume of 2.2 ft3. the lifting force on the balloon due to the outside air is the net resultant of the pressure distribution exerted on the exterior surface of the balloon. using this fact, we can derive archimedes’ principle, namely that the upward force on the balloon is equal to the weight of the air displaced by the balloon. assuming that the balloon is at sea level, where the air density is 0.002377 slug/ft3, calculate the maximum weight that can be lifted by the balloon. note: the molecular weight of air is 28.8 and that of helium is 4.