Q&A Hero

Q: The best time for digging clams (when the low tide is extra low) is during the time of the A) new or full moon. B) half moon. C) quarter moon. D) none of the above

Q: The Earth is closer to the Sun in January than in July, which accounts for the fact that the highest high tides in the Northern Hemisphere occur in A) winter. B) spring. C) summer. D) none of the above

Q: During an eclipse of the Sun the high ocean tides on Earth are A) extra high. B) extra low. C) not significantly different.

Q: On each given day and location, tides rise and fall at A) about the same time. B) exactly the same time. C) different times. D) ever increasing rates daily.

Q: If the Moon had twice as much mass and still orbits Earth at the same distance, ocean bulges on Earth would be A) smaller. B) larger. C) unequal in size. D) not significantly different. E) none of the above

Q: One side of the Moon continually facing Earth is A) a passing phenomenon. B) a cosmic coincidence. C) tidal lock.

Q: Tidal bulges on the Moon involve the concept of A) torques. B) elasticity. C) slight water on the Moon. D) magnetism.

Q: Tides caused mainly by the Moon occur in Earth's A) oceans. B) atmosphere. C) interior. D) all of the above

Q: Tidal forces in general are the result of A) two or more sources of gravitation. B) a combination of any kind of forces acting on a body. C) unequal forces acting on different parts of a body. D) the inverse-square law. E) unequal fluid flow.

Q: The main reason ocean tides exist is that Moon's pull is stronger A) than the pull of the Sun. B) on water closer to it than on water farther away. C) on Earth's oceans than on Earth itself. D) all of the above

Q: Which is most responsible for Earth's ocean tides? A) Moon B) Sun C) both contribute equally.

Q: Which pulls on the oceans of Earth with a greater force? A) Moon B) Sun C) both pull the same.

Q: When you step on a weighing scale at noon, Earth pulls you downward and the overhead Sun pulls you upward. The reason the Sun's pull doesn't decrease your weight at noon is because A) the Sun's pull on you is negligibly small. B) the weighing scale is calibrated only in Earth weight. C) you, the scale, and Earth are in free fall (in orbit) around the Sun. D) the Sun's pull is cancelled by the gravitation of other celestial bodies. E) of tidal effects in the "solid" Earth.

Q: If the Sun became twice as massive, your attraction to the Sun would double and your weight as measured on Earth would A) double. B) quadruple. C) not change.

Q: Passengers in a high-flying jumbo jet feel their normal weight in flight, while passengers in an orbiting space vehicle do not, because passengers in the space vehicle are A) beyond the main pull of Earth's gravity. B) above Earth's atmosphere. C) without support forces. D) all of the above E) none of the above

Q: Inside a freely-falling elevator, you would have no A) gravitational force on you. B) weight. C) both of these D) neither of these

Q: Inside a freely-falling runaway elevator, your A) acceleration is zero. B) weight is zero. C) gravitational interaction with Earth is zero. D) all of the above E) none of the above

Q: You experience weightlessness A) in the absence of a supporting surface. B) momentarily when you step off a chair. C) in a freely falling elevator. D) all of the above

Q: You can experience weight A) standing on Earth's surface. B) in an accelerating elevator away from Earth. C) in a rotating habitat in space. D) all of the above

Q: If you jounce up and down on a bathroom scale, what varies on the scale reading is A) mg. B) the normal force. C) both of these D) neither of these

Q: When you weigh yourself on a bathroom scale on a slight incline instead of a level surface, your weight reading on the scale will be A) less. B) no different. C) more.

Q: Your weight is the force A) due to gravity only. B) you exert against a supporting surface. C) equal to your normal force on any surface.

Q: The planet Jupiter is about 300 times as massive as Earth, yet on its surface you would weigh only about 3 times as much because A) your mass is 100 times less on Jupiter. B) Jupiter is significantly farther from the Sun. C) Jupiter's radius is about 10 times Earth's radius. D) you are 100 times more weightless there. E) none of the above

Q: The force of gravity acts on all apples on an apple tree. Some apples are twice as far from the ground as others. For the same mass these twice-as-high apples have A) 1/4 the weight. B) 1/2 the weight. C) practically the same weight.

Q: A weight watcher who normally weighs 400 N stands on top of a very tall ladder so she is one Earth radius above Earth's surface. How much is her weight there? A) 0 B) 100 N C) 200 N D) 400 N E) none of the above

Q: Two planets in space gravitationally attract each other. If both the masses and distances are doubled, the force between them is A) one-quarter. B) half as much. C) twice as much. D) four times as much. E) none of the above

Q: If Earth's mass decreased to one-half its original mass with no change in radius, then your weight would A) decrease to one-quarter. B) decrease to half. C) stay the same. D) none of the above

Q: When the distance between two stars decreases by one-third, the force between them A) decreases by one-third. B) decreases by one-half. C) increases to twice as much. D) increases to nine times as much. E) none of the above

Q: As two objects moving toward each other due to gravity get closer, the acceleration of each A) decreases. B) remains constant. C) increases.

Q: The force of Earth's gravity on a capsule in space increases as it comes closer. When the capsule moves to half its distance, the force toward Earth is then A) twice. B) three times greater. C) four times greater. D) none of the above

Q: The force of Earth's gravity on a capsule in space will lessen as it moves farther away. If the capsule moves to twice its distance, the force toward Earth becomes A) half. B) three-quarters. C) one-fourth. D) none of the above

Q: In comparison with other fundamental forces, the universal gravitational constant G indicates that gravity is A) very weak. B) strong. C) very strong.

Q: The universal gravitational constant G was first measured A) before Newton's time. B) by Newton himself. C) after Newton's time.

Q: The difference between Newton's law as a proportion and an equation involves A) the constant G. B) the equal sign. C) one being a vector and the other not. D) magnitude and direction.

Q: To make a profit a buyer purchases metal by weight at one altitude and sells it at the same price per pound at another altitude. The supplier should A) buy at a high altitude and sell at a low altitude. B) buy at a low altitude and sell at a high altitude. C) it makes no difference.

Q: If a block is set sliding on a huge imaginary frictionless plane in contact with Earth's surface, it will NOT sustain a constant speed because A) a component of gravitational force parallel to the plane soon acts on it. B) gravity gets weaker as distance increases. C) it is not free from the shackles of Earth's gravity. D) of its inertia.

Q: Two objects move toward each other due to gravity. As the objects get closer and closer, the force between them A) increases. B) decreases. C) remains constant.

Q: A very massive object A and a less massive object B move toward each other under the influence of gravity. Which force, if either, is greater? A) the force on A B) the force on B C) both forces are the same.

Q: If the Sun were twice as massive A) its pull on Earth would double. B) the pull of Earth on the Sun would double. C) both of these D) neither of these

Q: If the mass of Earth somehow increased with no change in radius, your weight would A) increase also. B) decrease. C) stay the same.

Q: What is the force of gravity on a 500-N woman standing on Earth's surface? A) 50 N B) 250 N C) 500 N D) 5000 N E) none of the above

Q: If Earth's radius somehow increased with no change in mass, your weight would A) increase also. B) decrease. C) stay the same.

Q: According to Newton, when the distance between two interacting objects doubles, the gravitational force is A) half. B) one-quarter. C) the same. D) twice as much. E) four times as much.

Q: According to Newton, the greater the masses of interacting objects, the A) less the gravitational force between them. B) greater the gravitational force between them. C) greater the force between them by the square of the masses.

Q: Newton discovered A) gravity. B) that gravity is universal. C) neither of these

Q: As you crawl toward the edge of a large freely-rotating horizontal turntable in a carnival funhouse, the angular momentum of you and the turntable A) decreases. B) increases. C) remains the same, but the revolutions per minute decrease. D) decreases in direct proportion to your decrease in revolutions per minute. E) none of these

Q: As the polar icecaps melt, the resulting water spreads over the entire Earth. This new mass distribution tends to make the length of a day A) longer. B) shorter. C) none of these

Q: If the planet Jupiter underwent gravitational collapse, its rate of rotation about its axis would A) decrease. B) increase. C) stay the same. D) need more information

Q: As a huge rotating cloud of particles in space gravitate together forming an increasingly dense ball, it shrinks in size and A) rotates slower. B) rotates at the same speed. C) rotates faster. D) cannot rotate.

Q: When you do somersaults, you'll more easily rotate when your body is A) straight with both arms above your head. B) straight with both arms at your sides. C) curled into a ball shape. D) no difference

Q: The chef at the infamous Fattening Tower of Pizza tosses a spinning disk of uncooked pizza dough into the air. The disk becomes wider during its flight, while its rotational speed A) remains constant. B) quickens. C) slows.

Q: When a twirling ice skater brings her arms inward, her rotational speed A) decreases. B) remains the same. C) increases.

Q: If the rotational speed of a rotating habitat in space increases, the weight experienced by occupants A) decreases. B) stays the same. C) increases. D) is always zero.

Q: A swimming area in a rotating space habitat is located in a region of 1/4 g. If a diver can jump 1 m high in a 1-g region, how high can the same diver jump in the swimming area? A) 1 m B) 2 m C) 4 m D) 16 m E) more than 16 m

Q: The gravitational field simulated by rotation in a space habitat that is best suited for humans is A) zero. B) g. C) one-quarter g. D) one-half g. E) three-quarters g.

Q: Multiple the equation for linear momentum by radial distance r and you have A) rotational kinetic energy. B) angular momentum. C) rotational inertia.

Q: A difference between linear momentum and angular momentum involves A) a radial distance. B) two types of speed. C) both of these D) neither of these

Q: The bob of a conical pendulum swings in a A) to-and-fro path. B) circular path. C) chaotic path.

Q: Centripetal force does no work on a circularly-moving object because A) no change in energy occurs. B) rotational energy transfers to kinetic energy. C) centripetal force has no component in the direction of motion. D) none of the above.

Q: The force responsible for a car moving steadily along a no-friction icy banked curve is due to A) centrifugal effects. B) the normal force at right angles to the curved surface. C) the radial component of the normal force. D) none of the above

Q: Centrifugal forces are an apparent reality to observers in a reference frame that is A) moving at constant velocity. B) an inertial reference frame. C) at rest. D) rotating. E) none of the above

Q: The main reason a person weighs less at the equator than at the poles involves the A) spin of the Earth. B) influence of the Sun, Moon, and all the planets. C) law of action and reaction.

Q: If you balance a broom horizontally on one finger, the center of gravity of the broom will be above your finger, closer to the bristles end than the handle end. If you saw the broom in two pieces at that point and weigh the two parts on a scale, you'll find that the heavier part is the A) bristles part. B) handle part. C) both the same weight

Q: You can safely stand on the overhanging end of a heavy plank that rests on a table. How much overhang depends on your mass and the mass of the plank. If you can stand on the end of a plank that overhangs the edge of the supporting table 1/5 its total length, how massive is the plank compared to your mass? A) 1/3 B) the same C) 2/3 D) 1 and 1/3 times E) more than 1 and 1/3 times

Q: You can safely stand on the overhanging end of a heavy plank that rests on a table. How much overhang depends on your mass and the plank's mass. If you can stand on the end of a plank that overhangs the edge of the supporting table 1/4 its total length, how massive is the plank compared to your mass? A) 1/2 B) the same C) 1 and 1/2 times D) twice E) 4 times

Q: A 1-kg rock is suspended from the tip of a horizontal meterstick at the 0-cm mark so that the meterstick barely balances like a seesaw when its fulcrum is at the 12.5-cm mark. From this information, the mass of the meterstick is A) 1/4 kg. B) 1/2 kg. C) 3/4 kg. D) 1 kg. E) none of the above

Q: A 1-kg rock is suspended from the tip of a horizontal meterstick at the 0-cm mark so that the meterstick barely balances like a seesaw when its fulcrum is at the 25-cm mark. From this information, the mass of the meterstick is A) 1/4 kg. B) 1/2 kg. C) 3/4 kg. D) 1 kg. E) none of the above

Q: When riding at constant velocity on a Segway electric vehicle, your center of mass is A) slightly in front of the point between wheels below. B) slightly behind the point between wheels below. C) directly above the point between wheels below.

Q: Strictly speaking, to weigh less in the Northern Hemisphere, you should move to a location farther A) north (toward the pole). B) south (toward the equator). C) east. D) west.

Q: If Earth rotated more slowly about its axis, your weight would A) increase. B) decrease. C) stay the same. D) be zero.

Q: To kick a football so it won't topple end over end, kick it so the force of impact extends A) above its center of gravity. B) through its center of gravity. C) below its center of gravity.

Q: If Earth had a pair of identical moons on opposite sides of the same circular orbit, the center of gravity of the double-moon-Earth system would be A) inside the Earth, but off center. B) at the center of the Earth. C) outside the Earth, but within the orbital path of the moons. D) outside the Earth, but beyond the orbital path of the moons.

Q: Which of these has its center of mass where no mass exists? A) baseball B) golf ball C) basketball D) none of the above

Q: The famous Leaning Tower of Pisa doesn't topple over because its center of gravity is A) relatively low for such a tall building. B) stabilized by its structure. C) displaced from its center. D) above a place of support. E) in the same place as its center of mass.

Q: The center of mass of a human body is located at a point that A) is fixed, but different for different people. B) is always directly behind the belly button. C) changes as a person bends over. D) none of the above

Q: The long, heavy tail of a spider monkey enables the monkey to easily vary its A) weight. B) momentum. C) inertia. D) center of gravity. E) none of the above

Q: Toss a baseball bat into the air and it wobbles about its A) geometrical center. B) center of mass. C) heavier end.

Q: A boy plays solitary seesaw by placing the seesaw's fulcrum one-eighth the distance from where he sits at one end. Which weighs more? A) the boy B) the seesaw C) they have equal weights D) need more information

Q: A solitary boy cannot balance on a seesaw with its fulcrum at its midpoint. If the fulcrum is moved to one-quarter the distance from the boy, balance is achieved when the weight of the boy is A) less than the weight of the seesaw. B) equal to the weight of the seesaw. C) more than the weight of the seesaw. D) need more information

Q: On a balanced seesaw, a boy three times as heavy as his partner sits A) less than 1/3 the distance from the fulcrum. B) 1/3 the distance from the fulcrum. C) more than 1/3 the distance from the fulcrum.