Q&A Hero

Q: If you lie on a bed of nails your back will encounter pressure due to contact with the nails. Nail pressure on your back will be less if the bed has A) fewer nails. B) more nails. C) both of the above D) none of the above

Q: Which will remain the same for two identical books, one lying flat and the other standing on an end? A) weight only B) pressure only C) both pressure and weight D) none of the above

Q: The concept of pressure involves both A) force and volume. B) force and area. C) area and volume.

Q: Your density is slightly greater when you are A) at the top of a mountain. B) submerged deep in water. C) in a fast-moving vehicle. D) none of the above

Q: The density of air at room temperature is about 1.2 g/cm3. Estimate the mass of air inside a 0.80-m3 volume refrigerator. (There are 1 million cm3 in 1 m3.) A) 0.96 g B) 960 kg C) 1000 kg D) more than 1000 kg

Q: The density of air at room temperature is about 1.2 g/cm3. This is the same as A) 12 kg/m3. B) 120 kg/m3. C) 1200 kg/m3.

Q: If the volume of an object doubles with no change in mass, its density would be A) half. B) double. C) unchanged.

Q: If we double the mass of an object without a change in volume, its density would be A) half. B) double. C) unchanged.

Q: Compared to the density of a kilogram of feathers, the density of a kilogram of lead is A) less. B) greater. C) the same.

Q: Which has the greater density, a lake full of water or a cupful of lake water? A) the cupful of lake water B) the lake C) both have the same density

Q: Compared to a bar of pure gold, the density of a pure gold ring is A) less. B) the same. C) greater.

Q: When a chocolate bar is cut in half, its density of each half is A) halved. B) unchanged. C) doubled.

Q: When a loaf of bread is compressed, its A) molecules decrease in size. B) density decreases. C) density increases. D) none of the above

Q: With no air resistance, a projectile fired at 60 has the same range as if it were fired at A) 15. B) 30. C) 45. D) 75.

Q: A projectile is launched at an angle of 15 above the horizontal and lands downrange. With no air resistance, what other projection angle for the same speed would produce the same downrange distance? A) 30 B) 45 C) 50 D) 75 E) 90

Q: A gun with a muzzle velocity of 100 m/s is fired horizontally from a tower. Neglecting air resistance, how far downrange will the bullet be 1 s later? A) 50 m B) 98 m C) 100 m D) 500 m E) none of the above

Q: A bullet fired horizontally hits the ground in 0.5 s. If it had been fired with twice the velocity it would have hit the ground in A) less than 0.5 s. B) more than 0.5 s. C) 0.5 s.

Q: A hunter aims a rifle at an angle of 10 below the horizontal. The hunter fires a bullet while simultaneously dropping another bullet from the side of the rifle. The bullet to hit the ground first is A) the dropped one. B) the fired one. C) both hit at the same time

Q: A hunter aims a rifle at an angle of 10 above the horizontal. The hunter fires a bullet while simultaneously dropping another bullet from the side of the rifle. The bullet to hit the ground first is A) the dropped one. B) the fired one. C) both hit at the same time

Q: A hunter fires a bullet from a horizontallyheld rifle while simultaneously dropping another bullet from the side of the rifle. The bullet to hit the ground first is A) the dropped one. B) the fired one. C) both hit at the same time

Q: A ball rolls off the edge of a table at the same time another ball drops vertically from the same table. The ball to hit the floor first is the A) rolling ball. B) dropped ball. C) both hit at the same time

Q: An object is thrown vertically into the air. Because of air resistance, the time for its descent will be A) longer than the ascent time. B) shorter than the ascent time. C) equal to the ascent time. D) not enough information

Q: A stone is thrown horizontally from the top of a cliff. One second after leaving your hand it drops a vertical distance of A) 5 m. B) 10 m. C) 15 m.

Q: If a projectile is fired straight up at a speed of 10 m/s, neglecting air resistance, the total time to return to its starting position is A) 1 s. B) 2 s. C) 10 s. D) 20 s. E) not enough information

Q: If a projectile is fired straight up at a speed of 10 m/s, neglecting air resistance, the time it takes to reach the top of its path is A) 1 s. B) 2 s. C) 10 s. D) not enough information

Q: A projectile is launched straight upward at 50 m/s. Neglecting air resistance its speed upon returning to its starting point is A) less than 50 m/s. B) 50 m/s. C) more than 50 m/s.

Q: A rock is thrown upward at 50 with respect to the horizontal. As it rises, its horizontal component of velocity A) increases. B) remains unchanged. C) decreases.

Q: A rock is thrown upward at 50 with respect to the horizontal. As it rises, its vertical component of velocity A) increases. B) remains unchanged. C) decreases.

Q: Nellie tosses a ball upward at an angle. Assuming no air resistance, which component of velocity changes with time? A) the horizontal component B) the vertical component C) both of these D) neither of these

Q: One second after a ball rolls off the edge of a horizontal surface at a speed of 10 m/s, A) its vertical component of velocity is 10 m/s. B) its speed is about 14 m/s. C) both of these D) none of the above

Q: With no air resistance a projectile fired horizontally maintains its horizontal component of velocity because A) no forces act on it. B) no horizontal forces act on it. C) of no initial vertical component of velocity. D) all of the above E) none of the above

Q: A bullet fired from a rifle begins to fall A) as soon as it leaves the barrel. B) after air friction reduces its speed. C) neither of these

Q: As a bowling ball that rolls off the edge of a table falls, its vertical component of motion A) decreases. B) remains constant. C) increases.

Q: As a bowling ball that rolls off the edge of a table falls, its horizontal component of motion A) decreases. B) remains constant. C) increases.

Q: A dropped ball gains speed because A) its velocity changes. B) a gravitational force acts on it. C) of inertia. D) its nature is to become closer to Earth.

Q: The identities of dark energy and dark matter are A) unknown at this time. B) subjects of intense astronomical interest. C) both of these D) neither of these

Q: This chapter states a link between Newton's Universal Law of Gravity and A) biological processes. B) chemical processes. C) geological processes. D) the U.S. Constitution. E) none of the above

Q: Dwarf planet Pluto was discovered by perturbations of A) Jupiter. B) Saturn. C) Uranus and Neptune. D) all of the above

Q: The planet Neptune was discovered by perturbations of A) Uranus. B) its moons. C) Pluto. D) none of the above

Q: Wobbles in the path of Uranus led to the discovery of A) Jupiter. B) Mars. C) Neptune. D) all of the above E) none of the above

Q: Planets wobble in their orbits due to A) the gravitational attraction to other planets. B) uncertainties in the inverse-square law. C) elliptical-orbit quirks. D) all of the above E) none of the above

Q: Perturbations of planets are due to A) interplanetary forces. B) deviations from straight-line paths. C) uneven masses of planets. D) none of the above

Q: An outcome of universal gravitation is that A) planets aren't cubes with sharp corners. B) its discovery prompted other laws of nature. C) it provided prediction and discovery of planets. D) all of the above

Q: The Sun is spherical due to A) Earth circling it. B) Earth and Moon circling it. C) gravitation. D) none of the above

Q: Weight can be simulated in a space vehicle if the vehicle is A) falling. B) in a circular orbit about Earth. C) rotating. D) none of the above

Q: Occupants of the International Space Station experience weightlessness due to A) the absence of Earth gravity at that altitude. B) the absence of a support force. C) rotation of the station. D) no inertia in space.

Q: Strictly speaking, when you step off a curb you are momentarily A) in orbit. B) weightless. C) in space.

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

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

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

Q: Your weight is equal to mg when you are A) firmly supported on a horizontal surface and in equilibrium. B) in Earth's gravitational field. C) anywhere except in Earth's orbit. D) all of the above

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

Q: How far away from Earth must one travel to completely be beyond Earth's gravity? A) to a region above the Earth's atmosphere B) to a region well beyond the Moon C) to a region beyond the solar system D) forget it; you can't travel far enough

Q: Each of us weighs slightly less inside the ground floor of a skyscraper than we do on the ground away from the skyscraper because the A) gravitational force is shielded inside the building. B) mass of the building attracts us upward slightly. C) both of these D) none of the above

Q: A supplier wants to make a profit by buying gold by weight at one altitude and selling it at the same price per newton 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) disregard altitude because it makes no difference.

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 10 times Earth's radius. D) you are 100 times more weightless there. E) none of the above

Q: The amount of gravitational force that acts on a space vehicle that orbits Earth is A) nearly zero. B) nearly as much as the vehicle's weight on Earth's surface. C) the same as the vehicle's weight on Earth's surface.

Q: At some point between Earth and the Moon, the forces due to gravity on a space traveler would be the same when this point is A) nearer Earth. B) nearer the Moon. C) mid-way between Earth and the Moon. D) none of the above

Q: In the vacuum of outer space far from our Sun, there is no A) gravity. B) atmospheric pressure. C) both of these D) none of the above

Q: A woman who normally weighs 400 N stands on top of a very tall ladder so she is one Earth-radius above Earth's surface. What is her weight there? A) zero B) 100 N C) 200 N D) 400 N 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. Such twice-as-high apples of the same mass, have A) 1/4 the weight. B) 1/2 the weight. C) practically the same weight.

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 on each other are the same

Q: If the masses of two planets doubles and the distance between them reduces by half, the force between them would be A) unchanged. B) half as much. C) twice as much. D) four times as much. E) none of the above

Q: If the masses of two planets doubles and the distance between them also doubles, the force between them would be 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, your weight would A) decrease to one-quarter. B) decrease to one-half. C) remain the same. D) none of the above

Q: If the radius of the Earth somehow increased with no change in mass, your weight would A) increase. B) not change. C) decrease.

Q: If the radius of the Earth somehow decreased with no change in mass, your weight would A) decrease. B) increase. C) not change.

Q: An object is placed exactly halfway between the Earth and the Moon. The object will fall toward the A) Earth. B) Moon. C) neither

Q: When the distance between a pair of stars doubles, the force between them A) decreases by one-quarter. B) decreases by one-half. C) increases to twice as much. D) increases to four times as much. E) stays the same.

Q: When the distance between a pair of stars decreases by half, the force between them A) decreases by one-quarter. B) decreases by one-half. C) increases to twice as much. D) increases to four times as much. E) stays the same.

Q: Two objects move toward each other due to gravity. As the objects get closer and closer, the acceleration of each A) increases. B) decreases. C) is not affected.

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: According to Newton, the closer gravitationally interacting objects are to each other, the A) less the gravitational force between them. B) more the gravitational force between them. C) constancy of the force between them.

Q: According to Newton, the greater the distance between gravitationally interacting objects, the A) less the gravitational force between them. B) more the gravitational force between them. C) constancy of the force between them.

Q: If the Sun were twice as massive, A) its pull on the Earth would double. B) Earth's pull on the Sun would double. C) both of these D) none of the above

Q: Consider two planets in space that gravitationally attract each other. If the masses of both planets are doubled, and the distance between them doesn't change, then 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: Consider two planets in space that gravitationally attract each other. If the mass of one planet is doubled, and the distance between them doesn't change, then 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