Q&A Hero

Q: The speeds of the planets about the Sun depend on A) their distances from the Sun. B) the masses of the planets. C) their periods of rotation. D) none of the above

Q: A lunar month is about 28 days. If the Moon were closer to Earth than it is now, the lunar month would be A) less than 28 days. B) about 28 days. C) more than 28 days. D) need more information

Q: A lunar month is about 28 days. If the Moon were farther from Earth than it is now, the lunar month would be A) less than 28 days. B) about 28 days. C) more than 28 days. D) need more information

Q: Our Moon in Earth orbit travels fastest when it is A) involved in an eclipse. B) rotating. C) revolving. D) closest. E) all of the above

Q: A weightless astronaut in an orbiting satellite is A) shielded from Earth's gravitational field. B) beyond the pull of gravity. C) like the satellite, pulled by Earth's gravitation. D) none of the above

Q: An astronaut at Earth's surface has a mass of 50 kg and a weight of 500 N. If she were floating freely inside a space habitat in remote space, she would have A) no weight and less mass. B) no weight and the same mass. C) more weight and no mass. D) none of the above

Q: It takes Neptune a longer time to orbit the Sun than Earth does because Neptune A) has much further to go. B) goes much slower. C) both of these D) none of these

Q: The fastest moving planet in a solar system is the A) smallest planet. B) most massive planet. C) planet nearest the Sun. D) planet farthest from the Sun. E) all move at the same speed.

Q: What prevents satellites such as the ISS from falling? A) gravity B) centripetal force C) centrifugal force D) the absence of air drag E) nothing

Q: Planets would crash into the Sun if it weren't for A) their tangential velocities. B) their vast distances from the Sun. C) the inverse-square law. D) their relatively small masses. E) the fact that they are beyond the main gravitation of the Sun.

Q: The Moon does not crash into Earth because A) Earth's gravitational field is relatively weak at the Moon. B) gravitational pull of other planets keeps the Moon up. C) Moon has a sufficient tangential speed. D) Moon has less mass than Earth. E) none of the above

Q: The radial velocity of an Earth satellite is its velocity A) parallel to the surface of Earth. B) perpendicular to the surface of Earth. C) attributed to satellites moving in any direction. D) none of the above

Q: The tangential velocity of an Earth satellite is its velocity A) parallel to the surface of Earth. B) perpendicular to the surface of Earth. C) attributed to satellites moving in any direction.

Q: An Earth satellite is simply a projectile A) freely falling around Earth. B) floating motionless in space near Earth. C) approaching Earth from outer space.

Q: While an airplane flies at 40 m/s at an altitude of 500 meters, the pilot drops a heavy package that falls to the ground. Neglecting air drag, about where does the package land relative to the plane flying above? A) directly beneath the plane B) 400 m behind the plane C) 500 m behind the plane D) more than 500 m behind the plane E) none of the above

Q: A bullet is fired horizontally with an initial velocity of 300 m/s from a 20-m high tower. If air resistance is negligible, the bullet hits downrange about A) 200 m. B) 300 m. C) 400 m. D) 500 m. E) 600 m.

Q: A ball player wishes to determine pitching speed by throwing a ball horizontally from an elevation 5 m above ground level. The ball lands 20 m downrange. The player's pitching speed is about A) 5 m/s. B) 10 m/s. C) 20 m/s. D) 25 m/s. E) none of the above

Q: An object is thrown vertically into the air. In this case air resistance affects motion. Compared with its time for ascent, the time for its descent is A) shorter. B) the same. C) longer. D) need more information

Q: Two projectiles are fired from ground level at equal speeds but different angles. One is fired at an angle of 30 and the other at 60. Neglecting air resistance, the projectile to hit the ground first will be the one fired at A) 30. B) 60. C) both hit at the same time

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 second later? A) 50 m B) 98 m C) 100 m D) 490 m E) none of the above

Q: Hang time is the time your feet are off the ground in a jump. If you jump upward inside a moving vehicle, your hang time will be A) slightly more. B) the same. C) slightly less.

Q: The paths of fragments of fireworks are A) normally straight lines. B) parabolas. C) different from the paths of projectiles.

Q: A bullet fired horizontally 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: It there were no gravity a stone thrown upward at 45 degrees would follow a straight-line path. But because of gravity, at the end of 1 second, the stone is actually A) 5 m below the straight line. B) 10 m below the straight line. C) 15 m below the straight line.

Q: If you throw a stone horizontally from the top of a cliff, one second after leaving your hand its vertical distance below the top of the cliff is A) 5 m. B) 10 m. C) 15 m.

Q: Ideally, a ball is thrown up at an angle and lands downrange. Because of air resistance, the distance reached is A) less. B) the same. C) greater. D) need more information

Q: When air drag affects the motion of projectiles, they don't travel A) as high. B) as far. C) both of these D) neither of these

Q: A projectile is launched vertically upward at 50 m/s. If air resistance does affect motion, then 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 projectile is launched vertically upward at 50 m/s. If air resistance is negligible, 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: An object is dropped and freely falls to the ground with acceleration g. If it is thrown upward at an angle instead, neglecting air drag, the acceleration along its path will be A) less than g. B) the same. C) more than g.

Q: After a rock thrown straight up reaches the top of its path and then falls a short distance, its acceleration is (neglect air resistance) A) greater than at the top of its path. B) less than at the top of its path. C) the same as at the top of its path.

Q: A ball is tossed upward. Neglecting air drag, the acceleration along its path is A) 0 g. B) g downward. C) g upward. D) g upward, then g downward. E) none of the above

Q: A projectile is fired into the air at an angle of 50 above ground level and hits a target downrange. It will also hit the target if fired at an angle of A) 40. B) 45. C) 55. D) 60. E) none of the above

Q: A projectile is launched from ground level at 15 above the horizontal and lands downrange. What other projection angle for the same speed would produce the same down-range distance? A) 30 B) 45 C) 50 D) 75 E) 90

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

Q: A hunter on level ground fires a bullet at an angle of 10 degrees below the horizontal while simultaneously dropping another bullet from the level of the rifle. Which bullet will hit the ground first? A) the one dropped B) the one fired C) both hit at the same time.

Q: A hunter on level ground fires a bullet at an angle of 10 degrees above the horizontal while simultaneously dropping another bullet from the level of the rifle. Which bullet will hit the ground first? A) the one dropped B) the one fired C) both hit at the same time.

Q: Dr. Chuck projects a ball horizontally from a lab bench. If the projection speed of the ball were greater, the time in the air would be A) less. B) the same. C) greater.

Q: Dr. Chuck projects a ball horizontally from a lab bench. The ball lands on a bullseye marked on the floor a horizontal distance equal to the ball's initial speed A) multiplied by its time in the air. B) coupled with its speed of fall. C) squared plus its downward speed squared when hitting the floor. D) all of the above E) none of the above

Q: Dr. Chuck projects a ball horizontally from a lab bench. The ball lands on a bullseye marked on the floor a horizontal distance away. Compared to the time for the ball to simply drop vertically from the bench, the time in the air for Dr. Chuck's projected ball is A) less. B) the same. C) greater.

Q: While a rock thrown upward at 50 degrees to the horizontal rises, neglecting air drag, its horizontal component of velocity A) increases. B) remains unchanged. C) decreases.

Q: While a rock thrown upward at 50 degrees to the horizontal rises, neglecting air drag, its vertical component of velocity A) increases. B) remains unchanged. C) decreases.

Q: A ball is thrown upward and caught when it returns. Compared with its initial speed and in the presence of air resistance, the speed with which it is caught is A) more. B) less. C) the same. D) need more information.

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: As soon as a ball rolls off the edge of a table A) it is not acted on by any forces. B) it is not acted on by any horizontal forces. C) has a zero net force acting on it. D) none of the above

Q: As soon as a bowling ball rolls off the edge of a table its horizontal component of velocity A) decreases. B) remains constant. C) increases.

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: 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: A ball rolled along a horizontal surface maintains a constant speed because A) its velocity remains constant. B) no horizontal force acts on it. C) of inertia.

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: Pluto is classified by as a A) full-fledged planet. B) dwarf planet. C) moon.

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

Q: Earth is presently accelerating toward the Sun (centripetal acceleration). If the Sun collapsed into a black hole, this acceleration would A) increase. B) decrease. C) remain the same. D) cease to exist.

Q: If the Sun collapsed to a black hole, Earth's gravitational attraction to it would be A) more. B) less. C) the same.

Q: When a star collapses to form a black hole, its mass A) increases. B) decreases. C) remains the same.

Q: The factor most directly responsible for making a black hole invisible is its A) size. B) mass. C) color. D) surface escape velocity. E) none of the above

Q: A black hole is A) an empty region of space with a huge gravitational field. B) at the center if all stars. C) the remains of a giant star that has undergone gravitational collapse.

Q: Which rocket would require more fuel? A) one going from the Moon to Earth. B) one going from Earth to the Moon. C) both the same.

Q: A hollow spherical planet is inhabited by people who live inside it, where the gravitational field is zero. When a very massive spaceship lands on the planet's surface, inhabitants find that the gravitational field inside the planet is A) still zero. B) non-zero, directed toward the spaceship. C) non-zero, directed away from the spaceship.

Q: Each of us weighs a tiny bit less inside the ground floor of a skyscraper than we do on the ground away from the skyscraper because the A) gravitational field is shielded inside the building. B) mass of the building above slightly attracts us upward. C) both of these D) neither of these

Q: Half-way to the center of a completely hollow planet with a thin uniform shell, your weight would be A) one-quarter of your weight on the surface. B) one-half of your weight on the surface. C) three-quarters of your weight on the surface. D) the same as at the surface. E) zero.

Q: Half-way to the center of a planet of uniform density, your weight compared to that at the surface would be A) one-quarter. B) one-half. C) three-quarters. D) the same as at the surface. E) zero.

Q: If you drop a stone into a hole drilled all the way to the other side of Earth (neglect the molten core), the stone will A) come to an abrupt stop at Earth's center. B) speed up until it gets to Earth's center. C) speed up until it reaches Earth's other side. D) slow down until it reaches Earth's center.

Q: The force of gravity acting on you will increase if you A) burrow deep inside Earth. B) stand on a planet with a shrinking radius. C) both of these D) neither of these

Q: How far must one travel to escape Earth's gravitational field? A) to a region above 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: If an object is placed exactly halfway between Earth and the Moon, it would fall toward the A) Earth. B) Moon. C) neither of these

Q: Rate this statement: No force due to Earth's gravity acts on astronauts inside the orbiting space station. A) always true while in orbit B) sometimes true while in orbit C) always false

Q: The amount of gravitational force that acts on a space vehicle while in Earth orbit 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: If your mass, the mass of Earth, and the mass of everything in the solar system were twice as much as it is now, yet everything stayed the same size, your weight on Earth would A) be the same. B) double. C) quadruple. D) be eight times as much as now. E) none of the above

Q: An asteroid exerts a 360-N gravitational force on a nearby spacecraft. If the spacecraft moves to a position three times as far from the center of the asteroid, the force will be A) zero. B) 40 N. C) 120 N. D) 360 N. E) 1080 N.

Q: An asteroid exerts a 360-N gravitational force on a nearby spacecraft. The 360-N force on the spacecraft is directed A) toward the asteroid. B) away from the asteroid. C) toward the Sun.

Q: The concept of force is fundamental to A) Newton's theory of gravitation. B) Einstein's theory of gravitation. C) both of these D) neither of these

Q: The direction of a gravitational field is A) in the same direction as gravitational attraction. B) away from the center of gravity of an object. C) opposite to the direction of gravitational attraction.

Q: Earth's gravitational field extends A) only above and beyond Earth's surface and cancels inside Earth. B) both inside and outside Earth and throughout the entire universe. C) neither of these

Q: Surrounding a magnet is a magnetic field. Surrounding an electron is an electric field. Surrounding Earth is A) an alteration in space in which mass experiences a force. B) a gravitational field. C) both of these D) neither of these

Q: All places on Earth would have high tides at the same instant if the A) Moon did not revolve. B) Moon did not rotate. C) Sun did not revolve. D) Sun did not rotate. E) none of the above

Q: There would be only one ocean tide per 24-hour day if the A) Earth and Moon were equally massive. B) Moon were more massive than Earth. C) Sun's influence on the tides were negligible. D) Moon's mass were small only a few kilograms. E) none of the above

Q: Suppose the Moon had twice the diameter but the same mass and same orbital distance from Earth. In that case, the high tides on Earth would be A) higher. B) lower. C) unequal in size. D) practically the same. E) none of the above