Minerals in volcanic rocks are usually smaller than minerals in plutonic rock. Why is this?
What will be an ideal response?
Answer: Volcanic rocks form at Earth's surface. Plutonic rocks form beneath Earth's surface. Because volcanic rock is extruded at the surface, it cools faster than plutonic rock. The shorter the cooling time, the smaller the crystals.
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In order to jump off the floor, the floor must exert a force on you
a. in the direction of and equal to your weight. b. opposite to and equal to your weight. c. in the direction of and less than your weight. d. opposite to and less than your weight. e. opposite to and greater than your weight.
LR Circuits: As shown in the figure, a circuit consists of a resistor R = 18 ? in series with an ideal inductor L = 33 H having no resistance. At time t = 0 s, there is a 12-A current in the circuit. When the magnetic energy of the inductor is 1600 J, what is the rate of dissipation of energy in the resistor?
A. 1700 W B. 440 W C. 870 W D. 1300 W E. 2200 W
Meteorites are important because
A) some come from the Moon and Mars, as well as the asteroid belt. B) they contain pristine material from the solar nebula. C) large ones may cause mass extinctions. D) All of the above are true. E) None of the above is true.
The focal length of the lens of a simple camera is 40.0 mm. How far must the lens be moved to change the focus of the camera from a person 25 m away to one that is 4.0 m away?
A) 0.2 mm B) 0.3 mm C) 0.4 mm D) 0.5 mm E) 0.7 mm