Q&A Hero

Q: If an object's mass is decreasing while a constant force is applied to the object, the acceleration A) decreases. B) increases. C) remains the same.

Q: A constant net force on a rail-road car produces constant A) velocity. B) acceleration. C) both of these D) neither of these

Q: A rock weighs 30 N on Earth and another rock weighs 30 N on the Moon. Which rock has the greater mass? A) the one on Earth B) the one on the Moon C) They have the same mass. D) not enough information

Q: When the bottom string is pulled slowly in the heavy-ball-and-strings demonstration (Figure 4.8 in your book), tension A) in the top string is due to your pull plus the weight of the ball. B) is about the same in both strings. C) in the bottom string is zero.

Q: A heavy ball hangs by a string, with a second string attached to its bottom. A slow pull on the bottom string breaks the A) top string. B) bottom string. C) top or bottom string equally.

Q: A heavy ball hangs by a string, with a second string attached to its bottom (Figure 4.8 in your book). A quick pull on the bottom string breaks the A) top string. B) bottom string. C) top or bottom string equally.

Q: When you stand at rest with your left foot on one bathroom scale and your right foot on a similar scale, each of the scales will A) read half your weight. B) read your weight. C) show readings that when added equal your weight. D) cancel your weight.

Q: At equilibrium on a bathroom weighting scale, the downward pull of gravity on you is balanced by A) your weight. B) an upward support force. C) your mass.

Q: In which case would you have the largest mass of gold? If your chunk of gold weighed 1 N on the A) Moon. B) Earth. C) planet Jupiter.

Q: Strange as it may seem, it is just as difficult to accelerate a car on a level surface on the Moon as it is here on Earth because A) the mass of the car is independent of gravity. B) the weight of the car is independent of gravity. C) both of these D) neither of these

Q: An object with twice as much mass as another object has twice as much A) inertia. B) speed. C) acceleration due to gravity. D) all of the above

Q: Your weight as measured on your bathroom scale is A) equal to your mass. B) the force due to gravity on you. C) a property of mechanical equilibrium. D) all of the above

Q: Compared to a 1-kg block of solid iron, a 2-kg block of solid iron has the same A) mass. B) volume. C) weight. D) all of the above E) none of the above

Q: Compared to a 1-kg block of solid iron, a 2-kg block of solid iron has twice as much A) inertia. B) mass. C) volume. D) all of the above E) none of the above

Q: Compared to the mass of an apple on Earth, the mass of the apple on the Moon is A) one sixth as much. B) the same. C) six times as much. D) zero.

Q: A bag of groceries that has a mass of 10 kilograms weighs about A) 1 N. B) 10 N. C) 100 N. D) 1000 N. E) greater than 1000 N.

Q: The mass of a pet turtle that weighs 10 N is about A) 1 kg. B) 10 kg. C) 100 kg. D) 1000 kg. E) none of the above

Q: The mass of a lamb that weights 110 N is about A) 1 kg. B) 11 kg. C) 110 kg. D) 1100 kg. E) none of the above

Q: A kilogram is a measure of an object's A) force. B) mass. C) both of these D) neither of these

Q: A 1-kg mass at the Earth's surface weighs A) 1 N. B) 5 N. C) 10 N. D) 12 N. E) none of the above

Q: Which has the greater mass? A) a king-size pillow B) an automobile battery C) both the same

Q: An object's weight is properly expressed in units of A) meters. B) kilograms. C) newtons. D) cubic centimeters.

Q: The newton is a unit of A) force. B) mass. C) density. D) inertia.

Q: A 300-kg bear grasping a vertical tree slides down at constant velocity. The friction force between the tree and the bear is A) 30 N. B) 300 N. C) 3000 N. D) more than 3000 N.

Q: A 10-N falling object encounters 10 N of air resistance. The net force on the object is A) 0 N. B) 4 N. C) 6 N. D) 10 N. E) none of these

Q: A 10-N falling object encounters 4 N of air resistance. The net force on the object is A) 0 N. B) 4 N. C) 6 N. D) 10 N. E) none of the above

Q: A mobile phone is pulled northward by a force of 10 N and at the same time pulled southward by another force of 15 N. The resultant force on the phone is A) 0 N. B) 5 N. C) 25 N. D) 150 N.

Q: If the net force on a cart is tripled, the cart's acceleration A) is one third. B) is two thirds. C) is three times as much. D) is more than three times as much.

Q: If you double the net force on an object, you'll double its A) acceleration. B) speed. C) velocity. D) all the above

Q: If an apple experiences a constant net force, it will have a constant A) velocity. B) speed. C) acceleration. D) position. E) more than one of the above

Q: Whenever the net force on an object is zero, its acceleration A) may be less than zero. B) is zero. C) may be more than zero.

Q: A skydiver's terminal velocity will be greatest if she falls A) head first. B) lying flat on her back. C) lying flat on her stomach. D) with her parachute open.

Q: A ball thrown straight upward takes 10 seconds for its up-and-down round trip. Because of air resistance, the time taken for the ball just to go up is A) less than 5 s. B) 5 s. C) more than 5 s.

Q: A ball is thrown vertically into the air. Because of air resistance, its time coming down compared to its time going up is A) less. B) the same. C) more.

Q: A ball is thrown upwards 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 always A) less. B) the same. C) more. D) can't be determined.

Q: A heavy rock and a light rock of the same size are falling through the air from a tall building. The one that encounters the greatest air resistance is the A) light rock. B) heavy rock. C) same for both

Q: Two tennis balls fall through the air from a tall building. One of them is filled with lead pellets. The ball to reach the ground first is the A) regular ball. B) lead-filled ball. C) same for both

Q: A ball is thrown vertically into the air. Because of air resistance, its speed when it returns to its starting level compared with its initial speed is A) less. B) the same. C) more.

Q: A 500-N parachutist opens his chute and experiences an air resistance force of 800 N. The net force on the parachutist is then A) 300 N downward. B) 500 N downward. C) 800 N downward. D) 300 N upward. E) 500 N upward.

Q: A skydiver steps from a helicopter and falls for a few seconds until terminal velocity is reached. Thereafter, until he opens his parachute, his acceleration A) is constant. B) increases. C) decreases. D) is zero. E) none of the above

Q: Suzie Skydiver jumps from a high-flying plane. As her velocity of fall increases, her acceleration A) increases. B) decreases. C) remains unchanged regardless of air resistance.

Q: A coconut and a bird's feather fall from a tree through the air to the ground below. The force of air resistance is A) greater on the coconut. B) greater on the feather. C) the same on each.

Q: A sack of potatoes weighing 200 N falls from an airplane. As the velocity of fall increases, air resistance also increases. When air resistance equals 200 N, the sack's acceleration becomes A) 0 m/s2. B) 5 m/s2. C) 10 m/s2. D) infinite. E) none of the above

Q: Suzie Skydiver, who weighs 500 N, reaches terminal velocity of 90 km/h. The air resistance on Suzie is then A) 90 N. B) 250 N. C) 410 N. D) 500 N. E) none of the above

Q: A large and a small person wish to parachute at equal terminal velocities. The larger person should A) get a larger parachute. B) jump lightly. C) pull upward on the supporting strands to decrease the downward net force. D) jump first from the plane.

Q: A river 100 m wide flows 1 m/s due south. A boat that travels 1 m/s relative to the water is pointed due east as it crosses from the west bank. Relative to its starting point, the boat travels A) nowhere. B) 100 m. C) 141 m. D) 200 m. E) more than 200 m.

Q: A river 100 m wide flows due south at 1 m/s. A boat that travels 1 m/s relative to the water is pointed due east as it crosses from the west bank. The boat reaches the east bank A) due east of its starting point. B) 100 m farther south. C) 141 m farther south. D) none of the above

Q: A motorboat that normally travels at 8 km/h in still water heads directly across a 6-km/h flowing river. The resulting speed of the boat is about A) 6 km/h. B) 8 km/h. C) 10 km/h. D) 20 km/h.

Q: A humming bird flying at 4 km/h that gets caught in a 3-km/h crosswind has a resultant speed of about A) 3 km/h. B) 4 km/h. C) 5 km/h. D) more than 5 km/h.

Q: A seagull flying at 10 km/h in a 10-km/h crosswind has a resultant speed of A) 10 km/h. B) about 14 km/h. C) 20 km/h. D) more than 20 km/h.

Q: A bird flying at 8 km/h in a 6-km/h crosswind has a resultant speed of A) 6 km/h. B) 8 km/h. C) 10 km/h. D) 14 km/h.

Q: An 80-km/h airplane caught in a 60-km/h crosswind has a resultant speed of A) 60 km/h. B) 80 km/h. C) 100 km/h. D) 141 km/h.

Q: An airplane that flies at 100 km/h in a 100-km/h crosswind has a ground speed of A) 0 km/h. B) 100 km/h. C) 141 km/h. D) 200 km/h.

Q: An 80-km/h airplane flying against a 10-km/h head wind has a groundspeed of A) 10 km/h. B) 70 km/h. C) 80 km/h. D) 90 km/h.

Q: An 80-km/h airplane flying in the same direction as a 10 km/h tail wind has a groundspeed of A) 10 km/h. B) 70 km/h. C) 80 km/h. D) 90 km/h.

Q: Which of the following is not a vector quantity? A) velocity B) speed C) acceleration D) all are vector quantities E) none are vector quantities.

Q: Phil leans over the edge of a cliff and throws a rock upward at 5 m/s. How far below the level from which it was thrown is the rock 2 seconds later? A) 5 m B) 10 m C) 15 m D) 20 m

Q: Phil leans over the edge of a cliff and throws a rock upward at 5 m/s. Neglecting air resistance, two seconds later the rock's speed is A) zero. B) 5 m/s. C) 10 m/s. D) 15 m/s. E) none of the above

Q: Phil leans over the edge of a cliff and throws a rock upward at 5 m/s. Neglecting air resistance, one second later the rock's speed is A) zero. B) 5 m/s. C) 10 m/s. D) 15 m/s. E) none of the above

Q: As water drops fall at a steady rate from a leaking faucet they A) get closer together. B) get farther apart. C) remain at a relatively fixed distance from one another.

Q: Compared with hang time on Earth, hang time on the Moon would be A) less. B) the same. C) greater.

Q: The vertical height attained by a basketball player who achieves a hang time of a full 1 s is about A) 0.8 m. B) 1 m. C) 1.2 m. D) 2.5 m. E) more than 2.5 m.

Q: A pot that falls from a ledge and hits the ground 45 m below hits the ground at A) 30 m/s. B) 60 m/s. C) 120 m/s. D) more than 120 m/s.

Q: A ball is projected 125 meters straight upward and then falls the same distance back to its starting point. Neglecting air resistance, its total time in the air is about A) 5 s. B) 10 s. C) 15 s. D) more than 20 s.

Q: Neglecting air resistance, a ball projected straight upward so it remains in the air for 10 seconds needs an initial speed of A) 50 m/s. B) 60 m/s. C) 80 m/s. D) 100 m/s. E) 110 m/s.

Q: Phil Physiker standing at the edge of a cliff throws one ball straight up and another ball straight down, both with the same speed. Neglecting air resistance, which ball hits the ground below with the greater speed? A) the one thrown upward B) the one thrown downward C) neither, both hit with the same speed

Q: A bullet is dropped into a river from a very high bridge at the same time as another bullet is fired straight downward from a rifle. Neglecting air resistance, the acceleration just before striking the water is A) greater for the dropped bullet. B) greater for the fired bullet. C) the same for each bullet. D) none of the above

Q: Neglecting air resistance, a bullet fired straight down from the top of a high cliff has an acceleration of A) less than 10 m/s2. B) 10 m/s2. C) more than 10 m/s2. D) depends on the height of the cliff.

Q: The muzzle velocity of a bullet fired from a new rifle is 100 m/s. Neglecting air resistance, at the end of one second a bullet fired straight up into the air will have traveled a distance of A) (100 - 5) m. B) (100 + 5) m. C) 100 m. D) 5 m. E) none of the above

Q: When a ball thrown straight upwards reaches the very top of its path, its acceleration is A) zero. B) 5 m/s2. C) 10 m/s2. D) none of the above

Q: Neglecting air resistance, how fast must you toss a ball straight up in order for it to take 6 seconds to return to its initial level? A) 5 m/s B) 10 m/s C) 20 m/s D) 30 m/s E) more than 30 m/s

Q: The total time it takes a projectile fired straight up at 10 m/s to reach the top of its path and return to its starting point is about A) 1 s. B) 2 s. C) 10 s. D) 20 s.

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

Q: If you throw a ball straight downward (in the absence of air resistance), after leaving your hand its acceleration is A) less than 10 m/s2. B) 10 m/s2. C) greater than 10 m/s2.

Q: An object falls freely from rest on a planet where the acceleration due to gravity is twice as much as on Earth. In the first 5 seconds it falls a distance of A) 100 m. B) 150 m. C) 250 m. D) 500 m. E) none of the above

Q: An object falls freely from rest on a planet where the acceleration due to gravity is 20 m/s2. After 5 seconds, the object will have a speed of A) 5 m/s. B) 10 m/s. C) 20 m/s. D) 50 m/s. E) 100 m/s.

Q: One half second after starting from rest, a freely falling object will have a speed of about A) 2 m/s. B) 5 m/s. C) 10 m/s. D) 20 m/s. E) none of the above

Q: The distance a freely falling object falls from rest in one-half second is A) 2 m. B) 4 m. C) 6 m. D) none of the above

Q: At one instant a heavy object in air is moving upward at 50 m/s. One second later its speed is approximately A) 40 m/s. B) 50 m/s. C) 55 m/s. D) 60 m/s.

Q: At one instant an object in free fall is moving downward at 50 m/s. One second later its speed is A) 25 m/s. B) 50 m/s. C) 55 m/s. D) 60 m/s. E) 100 m/s.