A 1.2-m high by 2.8-m wide vertical rectangular gate is used to control the flow of water from a reservoir to a grinding mill. A frictionless hinge runs along the bottom of the gate. The minimum force acting normal to and at the very top of the gate needed to hold the gate shut if the water is at the very top of the gate is nearest:
(A) 6590 N
(B) 9800 N
(C) 10 000 N
(D) 13 300 N
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Suppose we put a 0.3-kg hunk of ice at 0°C into an insulating thermos bottle filled with 1000 g of water at 20°C. What will be the system’s final temperature?
A. Below 0°C B. Almost exactly 0°C C. Somewhat above 0°C, but below 10°C D. Very roughly 10°C E. Somewhat below 20°C, but above 10°C F. Almost exactly 20°C
A parachutist jumping from an airplane reaches a terminal velocity when the force of air resistance is 980 N. The mass of the parachutist is
A. 980 kg. B. 220 lb. C. 100 kg. D. 100 lb. E. 980 lb.
How did Edwin Hubble measure the distance to the Andromeda Galaxy?
A) He measured its parallax. B) He used Cepheid variables in the Andromeda Galaxy. C) He deduced it from its redshift. D) He used white dwarf supernovae in the Andromeda Galaxy.
Most pulsars are known only as radio sources, but a few of the younger ones, like the Crab and Vela, also give off visible and even X-ray energy
Indicate whether the statement is true or false