Q&A Hero

Q: While you stand on the floor you are pulled downward by gravity, and supported upward by the floor. Gravity pulling down and the support force pushing up A) make an action-reaction pair of forces. B) do not make an action-reaction pair of forces. C) need more information

Q: When a baseball player bats a ball with a force of 1000 N, the reaction force that the ball exerts against the bat is A) less than 1000 N. B) more than 1000 N. C) 1000 N. D) need more information

Q: A player hits a ball with a bat. If action is the force of the bat against the ball, reaction is the A) air resistance on the ball. B) weight of the ball. C) force that the ball exerts on the bat. D) grip of the player's hand against the ball. E) weight of the bat.

Q: A player catches a ball. If action is the force of the ball against the player's glove, reaction is the A) player's grip on the glove. B) glove against the ball. C) friction of the ground against the player's shoes. D) muscular effort in the player's arms. E) none of the above

Q: The lift experienced by a helicopter involves an action-reaction pair of forces between the A) helicopter blades and the air. B) mass of the helicopter and Earth's mass. C) weight of the helicopter and atmospheric pressure. D) motion of the helicopter relative to the ground below. E) any or all of the above

Q: To produce an acceleration to a system there A) must be a net force on the system. B) may or may not be a net force on the system. C) must be acceleration outside the system also.

Q: The force that accelerates the orange and apple system featured in your textbook is actually supplied by the A) apple. B) orange. C) floor.

Q: The emphasis of the orange-and-apple sequence in your textbook is A) defining systems. B) actions equal reactions. C) forces produce accelerations. D) friction is a force. E) mass is not a force.

Q: When a karate chop breaks a board with a 3000-N blow, the amount of force that acts on the hand is A) zero. B) 1500 N. C) 3000 N. D) 6000 N.

Q: An archer shoots an arrow. Consider the action force to be the bowstring against the arrow. The reaction to this force is the A) combined weight of the arrow and bowstring. B) friction of the ground against the archer's feet. C) grip of the archer's hand on the bow. D) arrow's push against the bowstring.

Q: For every action force, there must be a reaction force that A) acts in the same direction. B) is slightly smaller in magnitude than the action force. C) is slightly larger in magnitude than the action force. D) is equal in magnitude.

Q: Action and reaction pairs of forces A) always act simultaneously. B) may or may not act simultaneously. C) are independent of time.

Q: Harry pulls on the end of a spring attached to a wall. The reaction to Harry's pull on the spring is A) the wall pulling oppositely on the spring. B) the spring pulling on Harry. C) both the wall and the spring pulling on Harry. D) none of the above

Q: When you walk, you push on the floor to the left and the floor A) also pushes on you to the left. B) pushes you to the right. C) both of these simultaneously. D) can only wish it could push on you. E) none of the above

Q: A fast-moving missile soaring overhead possesses A) speed. B) force. C) both of these D) neither of these

Q: A pair of action-reaction forces always A) act on the same object. B) occur simultaneously. C) comprise a pair of interactions. D) all of the above E) none of the above

Q: When a skateboarder pushes on a wall, A) an interaction occurs between the skateboarder and the wall. B) the wall pushes on the skateboarder. C) such a push couldn't happen unless the wall pushed on the skateboarder. D) all the above E) none of the above

Q: Arnold Strongman and Suzie Small each pull very hard on opposite ends of a rope in a tug-of-war. The greater force on the rope is exerted by A) Arnold, of course. B) Suzie, surprisingly. C) both the same, interestingly.

Q: The winner in a tug-of-war exerts the greatest force on A) the opponent. B) his or her end of the rope. C) the ground.

Q: A piece of rope is pulled by two people in a tug-of-war. Each exerts a 400-N force. What is the tension in the rope? A) zero B) 400 N C) 600 N D) 800 N E) none of the above

Q: One end of a rope is pulled with 100 N, while the opposite end also is pulled with 100 N. The tension in the rope is A) 0 N. B) 50 N. C) 100 N. D) 200 N.

Q: Your friend says that the heavyweight champion of the world cannot exert a force of 50 N on an isolated piece of tissue paper with his best punch. You A) agree that it can't be done. B) have reservations about this assertion. C) disagree, for a good punch easily delivers this much force.

Q: When a boxer hits a punching bag, the strength of his punch depends on how much force the bag can A) endure. B) exert on the boxer's fist. C) soften.

Q: As a ball bounces from a floor, its acceleration off the floor between bounces is A) significantly less than g. B) g. C) slightly more than g. D) significantly more than g.

Q: When you drop a rubber ball on the floor it bounces back. The force exerted on the ball to produce bouncing is by the A) ball. B) floor. C) need more information

Q: When you rub your hands together, you A) can push harder on one hand than the other. B) cannot push harder on one hand than the other. C) need more information

Q: You cannot exert a force on a wall A) if the wall resists. B) unless you put your mind to it. C) unless the wall simultaneously exerts the same amount of force on you.

Q: To say there is no such thing as only one force means A) there must also be a corresponding reaction force. B) other forces, perhaps not evident, are there. C) gibberish.

Q: A light woman and a heavy man jump from an airplane at the same time and open their same-size parachutes at the same time. Which person will get to the ground first? A) The light woman B) The heavy man C) Both should arrive at the same time. D) not enough information

Q: A light woman and a heavy man jump from an airplane at the same time and open their same-size parachutes at the same time. Which person will get to a state of zero acceleration first? A) The light woman B) The heavy man C) Both should arrive at the same time. D) not enough information

Q: Two objects of the same size, but unequal weights are dropped from a tall tower. Taking air resistance into consideration, the object to hit the ground first will be the A) lighter object. B) heavier object. C) Both hit at the same time. D) not enough information

Q: When a falling object has reached its terminal velocity, its acceleration is A) zero. B) g. C) constant.

Q: Two factors that greatly affect air resistance on falling objects are frontal area and A) mass. B) weight. C) speed.

Q: An astronaut on another planet drops a 1-kg rock from rest. The astronaut notices that the rock falls 2 meters straight down in one second. On this planet, how much does the rock weigh? A) 1 N B) 4 N C) 5 N D) 10 N

Q: A bowling ball and a baseball accelerate equally when falling in a vacuum because A) their velocities are the same. B) the ratio of their weights to mass is the same. C) the force of gravity is the same for each in a vacuum. D) the force of gravity does not act in a vacuum. E) none of the above

Q: A feather and a coin will have equal accelerations when falling in a vacuum because A) their velocities are the same. B) the force of gravity is the same for each in a vacuum. C) the force of gravity does not act in a vacuum. D) the ratio of both the feather's and coin's weight to mass is the same. E) none of the above

Q: Recall Galileo's Leaning Tower experiment. With negligible air resistance, a heavy and a light object fall A) with equal accelerations. B) with the same increases in speed. C) to the ground in equal times. D) all of the above

Q: A single brick falls with acceleration g. The reason a double brick falls with the same acceleration is A) that in free fall all accelerations are g. B) its ratio of force to mass is the same. C) an experimental fact tested many times. D) none of the above

Q: A 10-kg brick and a 1-kg apple are dropped in a vacuum. The force of gravity on the brick is A) the same as the force on the apple. B) 10 times more than the force on the apple. C) one-tenth as much as on the apple. D) zero.

Q: The human body can withstand an acceleration of 10 g under certain conditions. What net force would produce this acceleration for a 50-kg person? A) 500 N B) 2500 N C) 5000 N D) 25,000 N E) none of the above

Q: What horizontally-applied force will accelerate a 400-kg crate at 1 m/s2 across a factory floor against a friction force half its weight? A) 600 N B) 1600 N C) 2000 N D) 2400 N E) none of the above

Q: An astronaut on another planet drops a 1-kg rock from rest and finds that it falls a vertical distance of 2.5 meters in one second. On this planet, the rock has a weight of A) 1 N. B) 2 N. C) 3 N. D) 4 N. E) 5 N.

Q: A 2000-kg car experiences a braking force of 10,000 N and skids to a stop in 6 seconds. The speed of the car just before the brakes were applied was A) 1.2 m/s. B) 15 m/s. C) 30 m/s. D) 45 m/s. E) none of the above

Q: A 1000-kg automobile enters a freeway on-ramp at 20 m/s and accelerates uniformly up to 40 m/s in a time of 10 seconds. How far does the automobile travel during that time? A) 100 m B) 200 m C) 300 m D) 400 m E) none of the above

Q: If you are driving at 20 m/s and slam on your brakes and skid at 0.5g to a full stop, the skidding time is about A) 3 s. B) 4 s. C) 5 s. D) 6 s. E) greater than 6 s.

Q: A 10-kilogram block is pushed across a horizontal surface with a horizontal force of 20 N against a friction force of 10 N. The acceleration of the block is A) 1 m/s2. B) 2 m/s2. C) 5 m/s2. D) 10 m/s2. E) none of the above

Q: A 10-kilogram block with an initial velocity of 10 m/s slides 10 meters across a horizontal surface and comes to rest. It takes the block 2 seconds to stop. The stopping force acting on the block is about A) 5 N. B) 10 N. C) 25 N. D) 50 N. E) none of the above

Q: A car traveling at 22 m/s comes to an abrupt halt in 0.1 second when it hits a tree. What is the deceleration of the car? A) 110 m/s2 B) 220 m/s2 C) 800 m/s2 D) 880 m/s2 E) need more information

Q: An object released from rest on another planet requires one second to fall a distance of 6 meters. What is the acceleration due to gravity on this planet? A) 3 m/s2 B) 6 m/s2 C) 12 m/s2 D) 15 m/s2 E) none of the above

Q: Scotty Skydiver of mass 100 kg experiences air resistance of 500 N, and an acceleration of about A) 0.2 g. B) 0.3 g. C) 0.4 g. D) 0.5 g. E) greater than 0.5 g.

Q: The brakes of a speeding truck are slammed on and it skids to a stop. If the truck were heavily loaded so that it had twice the total mass, the skidding distance would be A) half as far. B) 1.5 times as far. C) twice as far. D) 4 times as far. E) the same.

Q: A 1-kg ball is thrown at 10 m/s straight upward. Neglecting air resistance, the net force that acts on the stone when it is halfway to the top of its path is about A) 1/2 N. B) 1 N. C) 5 N. D) 7.5 N. E) 10 N.

Q: If less horizontal force is applied to a sliding object than is needed to maintain a constant velocity, the object A) accelerates in the direction of the applied force. B) experiences decreased friction. C) eventually slides to a stop. D) none of the above

Q: If more horizontal force is applied to a sliding object than is needed to maintain a constant velocity, the object A) accelerates in the direction of the applied force. B) accelerates opposite the direction of the applied force. C) experiences greater friction. D) none of the above

Q: A 1-kg rock that weighs 10 N is thrown straight upward at 20 m/s. Neglecting air resistance, the net force that acts on it when it is half way to the top of its path is A) less than 10 N. B) 10 N. C) more than 10 N.

Q: A jumbo jet has a mass of 100,000 kg. The thrust for each of its four engines is 50,000 N. What is the jet's acceleration when taking off? A) 0.25 m/s2 B) 1 m/s2 C) 2 m/s2 D) 4 m/s2 E) none of the above

Q: Suppose a particle is being accelerated through space by a 10-N force. Suddenly the particle encounters a second force of 10 N in the opposite direction. The particle with both forces acting A) is brought to a rapid halt. B) decelerates gradually to a halt. C) continues at the speed it had when it encountered the second force. D) theoretically tends to accelerate toward the speed of light. E) none of the above

Q: A block is dragged without acceleration in a straight-line path across a level surface by a force of 6 N. What is the force of friction between the block and the surface? A) less than 6 N B) 6 N C) more than 6 N D) need more information

Q: A rock is thrown vertically into the air. At the top of its path, its acceleration is A) zero. B) 10 m/s2. C) between 0 and 10 m/s2. D) greater than 10 m/s2.

Q: A rock is thrown vertically into the air. At the top of its path the net force on it is A) less than mg. B) mg. C) more than mg.

Q: When a constant and sustained upward force acts on a rocket, its acceleration increases mainly because A) gravity becomes weaker with increased distance. B) the mass of the rocket decreases as fuel is burned. C) No way, for acceleration would be constant.

Q: A 10-N block and a 1-N block lie on a horizontal frictionless table. To impart equal horizontal accelerations, we would have to push the heavier block with A) an equal force. B) 10 times as much force. C) 10 squared or 100 times as much force. D) 1/10 as much force. E) none of the above

Q: A push on a 1-kg brick accelerates it. Neglecting friction, equally accelerating a 10-kg brick requires A) just as much force. B) 10 times as much force. C) 100 times as much force. D) one-tenth the amount of force. E) none of the above

Q: Phil stands at rest with both feet on a scale that reads 500 N. When he gently lifts one foot, the scale reads A) less than 500 N. B) 500 N. C) more than 500 N.

Q: Neglecting friction, a small and a large block of ice begin sliding down an incline together. The larger block reaches the bottom A) before the small block. B) after the small block. C) at the same time as the small block.

Q: A boulder following a straight-line path at constant velocity has A) a net force acting upon it in the direction of motion. B) zero acceleration. C) no forces acting on it. D) none of the above

Q: The force required to maintain a constant velocity for an astronaut in free space is equal to A) zero. B) the mass of the astronaut. C) the weight of the astronaut. D) the force required to stop the astronaut. E) none of the above

Q: A force of 1 N accelerates 1-kg box at the rate of 1 m/s2. The acceleration of a 2-kg box by a net force of 2 N is A) half as much. B) twice as much. C) the same. D) none of the above

Q: Nellie pulls on a 10-kg wagon with a constant horizontal force of 30 N. If there are no other horizontal forces, what is the wagon's acceleration? A) 0.3 m/s2 B) 3.0 m/s2 C) 10 m/s2 D) 30 m/s2 E) 300 m/s2

Q: A tow truck exerts a force of 3000 N on a car, which then accelerates at 2 m/s2. What is the mass of the car? A) 500 kg B) 1000 kg C) 1500 kg D) 3000 kg E) none of these

Q: A car has a mass of 1000 kg and accelerates at 2 m/s2. What net force is exerted on the car? A) 500 N B) 1000 N C) 1500 N D) 2000 N E) none of these

Q: If a non-rotating object has no acceleration, then we can say for certain that it is A) at rest. B) moving at constant non-zero velocity. C) in mechanical equilibrium. D) all of the above E) none of the above

Q: A heavy block at rest is suspended by a vertical rope. When the block accelerates upward by the rope, the rope tension A) is less than its weight. B) equals its weight. C) is greater than its weight.

Q: You drive your car at a constant 60 km/h along the highway. You apply the brakes until the car slows to 40 km/h. If at that moment you suddenly release the brakes, the car tends to A) momentarily regain its higher initial speed. B) continue moving at 40 km/h. C) decrease in speed if no other forces act.

Q: A car by itself is capable of a certain maximum acceleration. When it tows a twice-as-massive car, its maximum acceleration is A) one half. B) one third. C) one fourth. D) the same. E) none of these

Q: A car by itself is capable of a certain maximum acceleration. When it tows a car of the same mass, its maximum acceleration is A) one half. B) one third. C) one fourth. D) the same. E) none of these

Q: Which has zero acceleration? An object A) at rest. B) moving at constant velocity. C) in mechanical equilibrium. D) all of the above E) none of the above

Q: An apple at rest weighs 1 N. The net force on the apple when it is in free fall is A) 0 N. B) 0.1 N. C) 1 N. D) 9.8 N. E) none of the above

Q: An apple weighs 1 N. When the apple is held at rest above your head, the net force on the apple is A) 0 N. B) 0.1 N. C) 1 N. D) 9.8 N. E) none of the above

Q: If the mass of a cart is quickly loaded to have twice the mass while a propelling force remains constant, the cart's acceleration A) quadruples. B) doubles. C) stays the same. D) halves. E) none of these