Which of the following best describes the nature and origin of the atmospheres of the Moon and Mercury?
A) They have thin tropospheres only, with gas coming from evaporation and sublimation.
B) They have thin exospheres only, with gas coming from impacts of subatomic particles and photons.
C) They have only small amounts of gas, all of which is leftover from outgassing long ago.
D) They have very thin atmospheres produced by outgassing, but still have the layers of a troposphere, thermosphere, and exosphere.
B
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Slanting Surfaces With Friction: A flatbed truck is carrying a 20-kg crate up a sloping road. The coefficient of static friction between the crate and the bed is 0.40, and the coefficient of kinetic friction is 0.30. What is the maximum angle of slope that the truck can climb at constant speed if the crate is to stay in place?
A. 0.38° B. 13° C. 17° D. 22° E. 68°
A girl throws a stone from a bridge. Consider the following ways she might throw the stone. The speed of the stone as it leaves her hand is the same in each case, and air resistance is negligible
Case A: Thrown straight up. Case B: Thrown straight down. Case C: Thrown out at an angle of 45° above horizontal. Case D: Thrown straight out horizontally. In which case will the speed of the stone be greatest when it hits the water below? A) Case A B) Case B C) Case C D) Case D E) The speed will be the same in all cases.
A car enters a level, unbanked semi-circular hairpin turn of 100-m radius at a speed of 28 m/s. The coefficient of friction between the tires and the road is ? = 0.800 . If the car maintains a constant speed of 28 m/s, it will
a. attempt to dig into the road surface. b. tend to veer toward the center of the semicircle. c. arrive safely at the end of the semicircle. d. tend to veer toward the outside of the circle. e. veer toward the center for the first quarter-circle, then veer toward the outside for the second quarter-circle.
Two concentric imaginary spherical surfaces of radius R and 2R, respectively, surround a positive point charge Q located at the center of the surfaces. When compared to the electric flux ?1 through the surface of radius R, the electric flux ?2 through the surface of radius 2R is
A.
.B.
.C.
D.
E.