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Chapter 4 Newton’s Second Law of Motion A motorcycle undergoes acceleration when a. SF = 0. b. a nonzero net force acts on it. c. it is in equilibrium. d. All of these. A motorcycle undergoes acceleration when a. SF = 0. b. a nonzero net force acts on it. c. it is in equilibrium. d. All of these. When a net force acts on an object, its acceleration depends on the object’s a. initial speed. b. volume. c. weight. d. mass. When a net force acts on an object, its acceleration depends on the object’s a. initial speed. b. volume. c. weight. d. mass. Explanation: You could say acceleration depends on the object’s weight in most common instances, but mass is the more general answer. The force of friction between two surfaces can act a. only when the surfaces move relative to each other. b. whether or not the surfaces move relative to each other. c. even when the surfaces are far apart and not touching. d. only over microscopic distances. The force of friction between two surfaces can act a. only when the surfaces move relative to each other. b. whether or not the surfaces move relative to each other. c. even when the surfaces are far apart and not touching. d. only over microscopic distances. The force of air friction (air drag) against a falling sack of potatoes a. acts upward. b. increases with increased area. c. increases with increased speed. d. All of the above. The force of air friction (air drag) against a falling sack of potatoes a. acts upward. b. increases with increased area. c. increases with increased speed. d. All of the above. Mass is most closely related to a. inertia. b. weight. c. volume. d. location. Mass is most closely related to a. inertia. b. weight. c. volume. d. location. An object with a mass of 1 kilogram on Earth a. has less mass on the Moon. b. has the same mass on the Moon. c. has more mass on the Moon. d. weighs the same everywhere. An object with a mass of 1 kilogram on Earth a. has less mass on the Moon. b. has the same mass on the Moon. c. has more mass on the Moon. d. weighs the same everywhere. An object with a mass of 1 kilogram on Earth a. weighs less on the Moon. b. weighs the same on the Moon. c. weighs more on the Moon. d. weighs the same everywhere. An object with a mass of 1 kilogram on Earth a. weighs less on the Moon. b. weighs the same on the Moon. c. weighs more on the Moon. d. weighs the same everywhere. When we say that 1 kilogram weighs 10 N, we mean that a. 1 kg is 10 N. b. it’s true at Earth’s surface. c. it’s true everywhere. d. mass and weight are one and the same. When we say that 1 kilogram weighs 10 N, we mean that a. 1 kg is 10 N. b. it’s true at Earth’s surface. c. it’s true everywhere. d. mass and weight are one and the same. When your mass increases, your weight a. may remain the same. b. also increases. c. decreases. d. transforms to greater volume. When your mass increases, your weight a. may remain the same. b. also increases. c. decreases. d. transforms to greater volume. The force of gravity acting on a 2-kg melon is a. 2 kg. b. 10 N. c. 20 N. d. more than 20 N. The force of gravity acting on a 2-kg melon is a. 2 kg. b. 10 N. c. 20 N. d. more than 20 N. For a given force, acceleration and mass are a. b. c. d. directly proportional to each other. inversely proportional to each other. not related. two words for the same concept. For a given force, acceleration and mass are a. b. c. d. directly proportional to each other. inversely proportional to each other. not related. two words for the same concept. As mass is added to a pushed object, its acceleration a. b. c. d. increases. decreases. remains constant. quickly reaches zero. As mass is added to a pushed object, its acceleration a. b. c. d. increases. decreases. remains constant. quickly reaches zero. Explanation: Let the equation for Newton’s second law guide your answers! More mass means less acceleration. A cart is pushed and undergoes a certain acceleration. If it were pushed with twice the force while its mass doubles, its acceleration would be a. one-quarter. b. one-half. c. the same. d. nearly but not quite double. A cart is pushed and undergoes a certain acceleration. If it were pushed with twice the force while its mass doubles, its acceleration would be a. one-quarter. b. one-half. c. the same. d. nearly but not quite double. Explanation: Let the equation for Newton’s second law, a F/m, guide your answer. The ratios F/m and 2F/2m are the same. So acceleration is the same either way. A cart is pushed and undergoes a certain acceleration. If the force is held constant and the mass of the cart doubles, its acceleration would be a. one-quarter. b. one-half. c. the same. d. nearly but not quite twice. A cart is pushed and undergoes a certain acceleration. If the force is held constant and the mass of the cart doubles, its acceleration would be a. one-quarter. b. one-half. c. the same. d. nearly but not quite twice. During each second of free fall, the speed of an object a. increases by the same amount. b. changes by increasing amounts each second. c. remains constant. d. doubles each second. During each second of free fall, the speed of an object a. increases by the same amount. b. changes by increasing amounts each second. c. remains constant. d. doubles each second. The reason a 10-kg rock falls no faster than a 5-kg rock in free fall is that a. the 10-kg rock has greater acceleration. b. the 5-kg rock has greater acceleration. c. the force of gravity is the same for both. d. the force/mass ratio is the same for both. The reason a 10-kg rock falls no faster than a 5-kg rock in free fall is that a. the 10-kg rock has greater acceleration. b. the 5-kg rock has greater acceleration. c. the force of gravity is the same for both. d. the force/mass ratio is the same for both. Use Newton’s second law to answer this question: The acceleration of a vertically thrown ball at the top of its path is a. 0. b. 10 m/s2. c. between 0 and 10 m/s2. d. dependent on the initial speed of the ball. Use Newton’s second law to answer this question: The acceleration of a vertically thrown ball at the top of its path is a. 0. b. 10 m/s2. c. between 0 and 10 m/s2. d. dependent on the initial speed of the ball. Explanation: This question is a toughie for most people. At the top gravity still acts, so there’s a force on it. It still has mass. So in accord with a = F/m, a cannot be 0 as is popularly and wrongly asserted. The amount of air resistance that acts on a wingsuit flyer (and a flying squirrel) depends on the flyer’s a. area. b. speed. c. area and speed. d. acceleration. The amount of air resistance that acts on a wingsuit flyer (and a flying squirrel) depends on the flyer’s a. area. b. speed. c. area and speed. d. acceleration. A lead-filled tennis ball and a regular tennis ball are dropped from the top of a tall building at the same time. Air drag does affect motion. Which reaches the ground first? a. The lead-filled one. b. The regular one. c. They both reach the ground at the same time. d. No way to say. A lead-filled tennis ball and a regular tennis ball are dropped from the top of a tall building at the same time. Air drag does affect motion. Which reaches the ground first? a. The lead-filled one. b. The regular one. c. They both reach the ground at the same time. d. No way to say. Explanation: Like the falling parachutists in the text, the heavier one has a greater terminal speed and hits the ground first. A lead-filled tennis ball and a regular tennis ball are dropped from the top of a tall building. Air drag does affect motion. The ball that experiences the greater amount of air drag is the a. lead-filled one. b. regular one. c. Neither, for both experience the same amount of air resistance. d. No way to say. A lead-filled tennis ball and a regular tennis ball are dropped from the top of a tall building. Air drag does affect motion. The ball that experiences the greater amount of air drag is the a. lead-filled one. b. regular one. c. Neither, for both experience the same amount of air resistance. d. No way to say. Explanation: The faster ball of the same size experiences more air drag!