117. When a car rounds a curve to the right at high speed, the passengers experience the illusion of being acted upon by A. a centrifugal force directed to the right. B. a centrifugal force directed to the left. C. an upward-directed centrifugal force. D. an upward-directed centripetal force. E. a centripetal force directed to the left. 118. A centripetal force is one that is A. against the direction of motion of an object. B. directed toward the center of the Earth. C. directed toward the center of curvature of the path of a moving object. D. directed away from the center of curvature of the path of a moving object. E. in the direction of motion of an object. 119. When you whirl a rock tied to a string in a horizontal circle around your head, A. the rock exerts a centripetal force on the string. B. the string exerts a centripetal force on the rock. C. the Earth exerts a centripetal force on the rock. D. the string exerts a centripetal force on your hand. E. there are no centripetal forces involved. 120. When a car rounds a curve at high speed, A. the road exerts a centripetal force on the tires. B. the car body exerts a centripetal force on the tires. C. there are no centripetal forces involved. D. the car exerts a centripetal force on the road. E. the tires exert a centripetal force on the road. 121. When a car rounds a curve at high speed, A. there are no centripetal forces involved. B. the car exerts a centripetal force on the road. C. the tires exert a centripetal force on the road. D. the car exerts a centripetal force on the driver. E. the car body exerts a centripetal force on the tires. 122. As you whirl a rock tied to a string in a horizontal circle around your head, the string suddenly breaks; what happens? A. The rock will move inward and strike you on the head. B. The rock will move along a straight line tangent to the circle while curving toward the ground. C. The rock will move outward directly away from your head while curving toward the ground. D. The rock will continue to move in a circle about your head. E. The rock will fall straight to the ground._149. When air is removed from a metal can by a vacuum pump, the can buckles inwards and is crushed. This occurs because A. the air pressure on the outside of the can is greater than the air pressure on the inside of the can. B. the loss of air molecules from inside the can weakens the metal. C. the air pressure on the inside of the can is greater than the air pressure on the outside of the can. D. of Bernoulli's principle. E. the opposite sides of the empty can strongly attract each other. _150. A barometer made with mercury will be about 30 inches high while a barometer made with water will be about 34 feet high. This is because mercury and water have different A. accelerations. B. densities. C. volumes. D. colors. E. potential energies. _151. The air pressure at the top of a mountain is _ the air pressure at sea level because A. greater than; the air on the mountain top can press from all sides, rather than just from above. B. equal to; the air is in contact with the earth in both locations C. greater than; the air has more potential energy at the top of the mountain D. less than gravity is not as strong at the top of the mountain E. less than; there is less air above the mountain top _152. Bernoulli's principle says that when the speed of a fluid increases, A. pressure in the fluid decreases. B. the fluid does more work. C. gravitational potential energy of the fluid increases. D. pressure in the fluid increases. E. kinetic energy of the fluid decreases. 153. Bernoulli's principle explains why A. a hot air balloon rises. B. dead fish float. C. liquid rises in a drinking straw. D. submarines can remain submerged. E. airplanes fly. 154. An airplane wing is shaped such that A. air flows more rapidly across the bottom than over the top of the wing. B. air flows more rapidly over the top than across the bottom of the wing. C. air does not flow over the top of the wing. D. air flows at the same rate across the bottom and over the top of the wing. E. air does not flow across the bottom of the wing. 23_162. According to Boyle's Law, if the volume occupied by a certain gas is doubled, A. the number of atoms in the gas will be halved. B. the pressure of the gas will remain constant. C. the pressure of the gas will be doubled. D. the pressure of the gas will be quadrupled. E. the pressure of the gas will be halved. _163. According to Boyle's Law, if the volume occupied by a certain gas is halved, A. the pressure of the gas will be halved. B. the number of atoms in the gas will be doubled. C. the pressure of the gas will be quadrupled. D. the pressure of the gas will be doubled. E. the pressure of the gas will remain constant. _164. When a fixed amount of air is compressed, at constant temperature, to half its original volume, A. the pressure of the air will be twice as much as before. B. the density of the air will be one half as much as before. C. the pressure of the air will be four times as much as before. D. the pressure of the air will be one half as much as before. E. the density of the air will be one fourth as much as before. 165. When a fixed amount of air is compressed, at constant temperature, to one fourth its original volume, A. the pressure of the air will be twice as much as before. B. the pressure of the air will be one fourth as much as before. C. the density of the air will be one half as much as before. D. the density of the air will be one fourth as much as before. E. the pressure of the air will be four times as much as before. 166. When a fixed amount of air is compressed, at constant temperature, to one third its original volume, A. the pressure of the air will be three times as much as before. B. the pressure of the air will be nine times as much as before. C. the density of the air will be one third as much as before. D. the pressure of the air will be one third as much as before. E. the density of the air will be nine times as much as before. 167. Archimedes' Principle states that an object surrounded by air is buoyed up by a force equal to the A. weight of the air it displaces. B. weight of Archimedes. C. total pressure on the object. D. difference between the weight of the object and the weight of the air it displaces. E. weight of the object.168. A balloon will cease rising in air only when A. the buoyant force on the balloon equals the weight of the balloon. B. the buoyant force on the balloon is zero. C. the weight of the balloon is zero. D. the air pressure is zero. E. the balloon reaches the very top of the atmosphere. _169. Two helium-filled balloons have the same mass but one is larger than the other. Which will rise more rapidly in air? A. The larger one, because it has a greater buoyant force. B. They will rise at the same rate because they both contain helium. C. The smaller one, because it has a greater buoyant force. D. The smaller one, because it has a higher density. E. The larger one, because it has a higher density. _170. Two lighter-than-air helium-filled containers have the same fixed volume but one holds twice as many helium atoms as the other. Which will rise more rapidly in air? A. The one with more helium, because it has a higher density. B. The one with less helium, because it has a greater buoyant force. C. The one with more helium, because it has a greater buoyant force. D. The one with less helium, because it has a lower weight. E. They will rise at the same rate because they both contain helium. 171. Humans generally do not rise into the air like helium-filled balloons because A. our bodies contain bones. B. our bodies contain no helium. C. our bodies are more dense than air. there is no buoyant force acting on our bodies. E. air pressure pushes us down onto the ground. _172. On which of these would air produce the greatest buoyant force? A. a flying robin B. an elephant C. a cat a perching robin a flying mosquito 173. A helium-filled balloon released at the Earth's surface rises into the air. If an identical helium-filled balloon were released at the surface of the Moon, where there is less gravity and no atmosphere, what would happen to the balloon? A. The balloon would rise from the Moon's surface, but at a slower rate than it did on Earth. B. The balloon would rise from the Moon's surface, but at a faster rate than it did on Earth. C. The balloon would rise from the Moon's surface at the same rate as it did on Earth. D. The balloon would fall to the Moon's surface. E . The balloon would hover above the Moon's surface