Stephen Hawking predicted that black holes can "evaporate" by emitting what we now call Hawking radiation. What does it mean for a black hole to "evaporate"?
A) The black hole loses its electric charge.
B) The black hole's mass is gradually reduced.
C) The black hole itself remains unchanged in mass, but it is able to send radiation out into the universe.
D) Any matter that surrounds the black hole is heated to the point where it becomes a gas, if it wasn't already.
B) The black hole's mass is gradually reduced.
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Friction: A bulldozer attempts to drag a log weighing 500 N along the rough horizontal ground. The cable attached to the log makes an angle of 30° above the ground. The coefficient of static friction between the log and the ground is 0.50, and the coefficient of kinetic friction is 0.35. What minimum tension is required in the cable in order for the log to begin to slide?
Fill in the blank(s) with the appropriate word(s).
A 14-A current flows into a series combination of a 3.0-? and a 4.0-? resistor. What is the voltage drop across the 4.0-? resistor?
A) 24 V B) 38 V C) 42 V D) 56 V E) 98 V
Shear Modulus: The base of a metal block, which is fixed in place, measures 90 cm by 90 cm, and the height of the block is 60 cm. A force, applied to the upper face and parallel to it, produces a shear strain of 0.0060. The shear modulus of this metal is 3.0 × 1010 Pa. The shear stress on the block in megapascals is closest to
A. 180 MPa. B. 360 MPa. C. 600 MPa. D. 720 MPa. E. 900 MPa.
Fluorescent minerals on display in museums are illuminated with
A) infrared light. B) ultraviolet light. C) often either or both D) none of these