Q&A Hero

Q: A ball is thrown upwards and returns to the same location. Compared with its initial speed its speed when it returns is about A) half as much. B) the same. C) twice as much. D) four times as much.

Q: An object at rest near the surface of a distant planet starts to fall freely. If the acceleration there is twice that of the Earth, its speed one second later would be A) 10 m/s. B) 20 m/s. C) 30 m/s. D) 40 m/s.

Q: If an object falling freely were somehow equipped with an odometer to measure the distance it travels, then the amount of distance it travels each succeeding second would be A) constant. B) less and less each second. C) greater than the second before. D) doubled.

Q: If a freely falling object were equipped with a speedometer on a planet where the acceleration due to gravity is 20 m/s2, then its speed reading would increase each second by A) 10 m/s. B) 20 m/s. C) 30 m/s. D) 40 m/s. E) depends on its initial speed

Q: If a freely falling object were equipped with a speedometer, its speed reading would increase each second by about A) 5 m/s. B) 10 m/s. C) 15 m/s. D) a variable amount. E) depends on its initial speed

Q: If a stone falls to the bottom of a mineshaft in 6 seconds, then the depth of the shaft is about A) 60 m. B) 120 m. C) 180 m. D) more than 200 m.

Q: An apple falls from a tree and hits the ground 5 meters below with a speed of about A) 5 m/s. B) 10 m/s. C) 15 m/s. D) 20 m/s. E) not enough information

Q: Twelve seconds after starting from rest, a freely-falling cantelope has a speed of A) 10 m/s. B) 50 m/s. C) 100 m/s. D) more than 100 m/s.

Q: The distance a freely falling bowling ball falls each second A) is about 5 m. B) is about 10 m. C) increases. D) none of the above

Q: While an iron block near the Earth's surface is in free fall, it undergoes an increase in A) speed. B) acceleration. C) both of these D) neither of these

Q: A freely-falling watermelon falls with constant A) velocity. B) speed. C) acceleration. D) distances each successive second.

Q: The accelerations possible for a ball on an inclined plane A) range from zero to g. B) range from g to infinity. C) have no limit.

Q: If a rocket initially at rest accelerates at a rate of 50 m/s2 for one minute, its speed will be A) 50 m/s. B) 500 m/s. C) 3000 m/s. D) 3600 m/s.

Q: Ten seconds after starting from rest, a car is moving at 40 m/s. What is the car's acceleration? A) 0.25 m/s2 B) 2.8 m/s2 C) 4.0 m/s2 D) 10 m/s2 E) 40 m/s2

Q: What is the acceleration of a car that starts from rest and 5 seconds later reaches a speed of 20 m/s? A) 1 m/s2 B) 2 m/s2 C) 3 m/s2 D) 4 m/s2 E) 5 m/s2

Q: The time it takes a car to attain a speed of 30 m/s when accelerating from rest at 2 m/s2 is A) 2 s. B) 15 s. C) 30 s. D) 60 s. E) none of the above

Q: A ball starting from rest at the top of an inclined plane accelerates at 2 m/s2 and reaches the bottom of the plane in 3 seconds. What is the length of the plane? A) 2 m B) 3 m C) 5 m D) 9 m

Q: A ball starting from rest at the top of an inclined plane gains a speed of 2 m/s for each second it rolls. What is its acceleration down the incline? A) 0.5 m/s2 B) 1 m/s2 C) 2 m/s2 D) 4 m/s2

Q: A car's speed 3 seconds after accelerating from rest at 2 m/s2 is A) 2 m/s. B) 3 m/s. C) 4 m/s. D) 6 m/s.

Q: A ball tossed vertically upward rises, reaches its highest point, and then falls back to its starting point. During this time the acceleration of the ball is always A) in the direction of motion. B) opposite its velocity. C) directed upward. D) directed downward. E) none of the above

Q: A rock dropped from a 5-m height accelerates at 10 m/s2 and strikes the ground 1 s later. If the rock is dropped from a height of 2.5 m, its acceleration of fall is A) half. B) the same. C) twice. D) four times as much.

Q: If an object moves with constant acceleration, its velocity must A) be constant also. B) change by the same amount each second. C) change by varying amounts depending on its speed. D) always decrease.

Q: A cart changes its speed from 90 m/s to 100 m/s in 10 seconds. During this interval its acceleration is A) zero. B) 1 m/s2. C) 10 m/s2. D) none of the above

Q: A cart maintains a constant velocity of 100 m/s for 10 seconds. During this interval its acceleration is A) zero. B) 1 m/s2. C) 10 m/s2. D) none of the above

Q: An object covers a distance of 8 meters in the first second of travel, another 8 meters during the next second, and 8 meters again during the third second. Its acceleration is A) 0 m/s2. B) 5 m/s2. C) 8 m/s2. D) 24 m/s2.

Q: If a car increases its velocity from zero to 60 m/s in 10 seconds, its acceleration is A) 3 m/s2. B) 6 m/s2. C) 60 m/s2. D) 600 m/s2.

Q: While a car travels around a circular track at a constant speed, its A) acceleration is zero. B) velocity is zero. C) inertia is zero. D) none of the above

Q: A ball rolls along a horizontal track in a certain time. If the track has a small upward dent in it, the time to roll the length of the track will be A) less. B) the same. C) more.

Q: A ball rolls along a horizontal track in a certain time. If the track has a dip in it, the time to roll the length of the track will be A) less. B) the same. C) more.

Q: The average speed of a horse that gallops 10 kilometers in 30 minutes is A) 15 km/h. B) 20 km/h. C) 30 km/h. D) 40 km/h.

Q: A vehicle undergoes acceleration when it A) gains speed. B) loses speed. C) changes its direction. D) all of the above

Q: When you walk at an average speed of 4 m/s, in 5 s you'll cover a distance of A) 2 m. B) 10 m. C) 15 m. D) 20 m.

Q: The two measurements necessary for calculating average speed are A) acceleration and time. B) velocity and time. C) distance and time. D) distance and acceleration. E) velocity and distance.

Q: The speedometer of an automobile reads A) average speed. B) instantaneous speed. C) accelerated speed.

Q: Jogging Jake runs at 4 m/s along a train flatcar that moves at 10 m/s in the opposite direction. Jake's speed relative to the ground is A) 6 m/s. B) 10 m/s. C) 14 m/s. D) none of the above

Q: Jogging Jake runs at 4 m/s along a train flatcar that moves at 10 m/s in the same direction. Jake's speed relative to the ground is A) 6 m/s. B) 10 m/s. C) 14 m/s. D) none of the above

Q: You're at rest in a hammock when a hungry mosquito sees an opportunity for lunch. A mild 2-m/s breeze is blowing. If the mosquito joins you for lunch it should hover over you by flying A) against the breeze at 2 m/s. B) with the breeze at 2 m/s. C) a bit faster than wind speed. D) none of the above

Q: Katelyn runs along the aisle of a train that moves at 8 m/s. Her speed relative to the floor is 3 m/s. Her speed relative to an observer at rest on the ground is A) 5 m/s. B) 11 m/s. C) either depending on her running direction D) none of the above

Q: A mosquito flying at 3 m/s that encounters a breeze blowing at 3 m/s in the opposite direction has a speed of A) 0 m/s. B) 3 m/s. C) 4 m/s. D) 6 m/s.

Q: A mosquito flying at 3 m/s that encounters a breeze blowing at 3 m/s in the same direction has a speed of A) 0 m/s. B) 3 m/s. C) 4 m/s. D) 6 m/s.

Q: A bird sitting on the limb of a tree is moving about 30 km/s with respect to the Sun. If the bird takes 1 second to drop down to a worm below, the worm would be 30 km downrange from the bird when it reached the ground. This faulty reasoning is best countered with Newton's A) law of inertia. B) law of gravity. C) laws of motion. D) none of the above

Q: Earth continually moves about 30 km/s through space, which means the wall you stand next to also is moving at 30 km/s. When you jump vertically the wall doesn't slam into you because A) the speeds of you and Earth cancel out. B) you're moving horizontally just as fast as the wall. C) your upward motion is small compared with Earth's speed. D) motion of the Sun counteracts your motion.

Q: A gymnast performing somersaults in a high-flying plane moving at constant velocity needs to make A) small adjustments to compensate for the airplane's velocity. B) major adjustments to compensate for the airplane's velocity. C) no adjustments. D) none of the above

Q: If you toss a coin straight upward in train that slows while the coin is in the air, the coin will land A) as if you were at rest. B) in front of you. C) in back of you.

Q: If you toss a coin straight upward in train that gains speed while the coin is in the air, the coin will land A) as if you were at rest. B) in front of you. C) in back of you.

Q: If you toss a coin straight upward while in a train moving at constant velocity, the coin will land A) as if you were at rest. B) in front of you. C) in back of you.

Q: The force that causes Earth to orbit the Sun is due to gravity, while the force needed to keep Earth moving as it circles the Sun is A) inertia. B) due to gravity. C) due to both inertia and gravity. D) no force at all.

Q: An 800-N man stands at rest on two bathroom scales so that his weight is distributed evenly over both scales. The reading on each scale is A) 200 N. B) 400 N. C) 800 N. D) 1600 N. E) none of the above

Q: Weigh yourself on a weighing scale and the scale shows your normal weight. If you carefully stand on tiptoes, the scale reading will be A) slightly more. B) slightly less. C) about half as much. D) no different.

Q: When you stand at rest on a pair of bathroom scales, the reading on each scale A) is half your weight. B) equals your weight. C) add up to equal your weight.

Q: The support force on a 30-kg dog sleeping on the floor is A) less than 300 N. B) about 300 N. C) more than 300 N. D) nonexistent while asleep.

Q: Jason weighs 150 N and sits on his big brother's shoulders. Big brother weighs 400 N. The support force supplied by the floor must be A) 150 N. B) 400 N. C) 550 N. D) more than 550 N.

Q: The support force on a 10-N book at rest on a table is A) slightly less than 10 N. B) 10 N. C) slightly greater than 10 N. D) dependent on the position of the book.

Q: The minimum number of forces that act on a book resting on a table is A) 1. B) 2. C) 3. D) 4. E) none of the above

Q: The force of friction on a sliding object is 10 N. The applied force needed to maintain a constant velocity is A) more than 10 N. B) less than 10 N. C) 10 N.

Q: The net force acting on an insect falling downward at constant velocity is A) zero. B) the weight of the insect. C) upward air resistance. D) none of the above

Q: A hockey puck sliding at constant velocity across the ice is A) in equilibrium. B) nearly in equilibrium. C) is nowhere near being in equilibrium. D) none of the above

Q: Burl and Paul have a total weight of 1300 N. The tensions in the supporting ropes that support their scaffold add to 1700 N. The weight of the scaffold itself must be A) 300 N. B) 400 N. C) 500 N. D) 600 N.

Q: Burl and Paul paint signs together on a scaffold. Compared to their weights plus the weight of the scaffold, the sum of tensions in the supporting ropes is A) less. B) the same. C) greater. D) zero.

Q: If Burl carries Paul piggy-back while standing in the middle of a scaffold, the tensions in the two supporting ropes would A) cancel to zero. B) be equal. C) be in dynamic equilibrium. D) more easily support Burl and Paul.

Q: When Burl and Paul stand on opposite ends of a sign-painting scaffold, the tensions in the supporting ropes A) are equal. B) depend on the relative weights of Burl and Paul. C) combine to equal zero. D) are in equilibrium.

Q: An object in mechanical equilibrium is an object A) moving with constant velocity. B) having no changes in velocity. C) at rest. D) all of the above

Q: The equilibrium rule applies to A) vector quantities. B) quantities that are equal in magnitude. C) scalar quantities. D) any kind of quantities.

Q: The equilibrium rule, ΣF = 0, applies to A) objects or systems at rest. B) objects or systems in uniform motion in a straight line. C) both of these D) neither of these

Q: The net force on any object in equilibrium is A) zero. B) equal to its weight. C) less than its weight. D) non-zero when motion is involved.

Q: Nellie hangs from a pair of ropes at an angle. Tension in the ropes depends on the A) length of the ropes. B) angle of the ropes. C) both of these D) neither of these

Q: Monkey Mo hangs from the middle of a horizontal rope. Tension in the rope is greatest if the rope A) sags a lot. B) sags very little. C) sags or doesn't sag, for tension is the same in any case. D) none of the above

Q: When Nellie Newton hangs at rest in the middle of a clothesline, the tension will not be the same in each side of the rope when A) the lengths of rope on each side are different. B) the angles at each side of the rope are unequal. C) she is in equilibrium. D) none of the above

Q: When Nellie Newton hangs at rest in the middle of a clothesline, tensions will be the same in each side of the rope when A) the lengths of each rope are the same. B) the angles for both sides of the rope are equal. C) she is in equilibrium.

Q: Suspend your body from a pair of ropes slightly angled from the vertical and the tension in each rope will be A) equal your weight. B) half your weight. C) greater than half your weight. D) none of these

Q: Suspend your body from a pair of vertical ropes and the tension in each rope will be A) half your weight. B) equal to your weight. C) greater than your weight. D) none of the above

Q: A pair of wires support a heavy painting. Tension in the wires is greater when they are A) vertical. B) not vertical. C) the same regardless of the wire orientation. D) none of the above

Q: A parallelogram is a four-sided figure with opposite sides that are A) equal. B) parallel. C) at right angles. D) none of the above

Q: If Nellie hangs from a horizontal bar that is supported by four vertical ropes, the tension in the ropes A) are each half her weight. B) are each equal to her weight. C) add to equal her weight. D) none of the above

Q: When Nellie Newton hangs by the ends of a rope draped over a large pulley, the tension in each supporting vertical strand is A) half her weight. B) equal to her weight. C) twice her weight. D) none of the above

Q: The resultant of a 40-N force at right angles to a 30-N force is A) 30 N. B) 40 N. C) 50 N. D) greater than 50 N.

Q: A pair of 10-N vectors at right angles to each other has a resultant of about A) 10 N. B) 14 N. C) 20 N. D) none of the above

Q: When a pair of 10-N forces act on a box of candy, the net force on the box is A) zero. B) about 14 N. C) 20 N. D) Any of the above depending on the directions of forces.

Q: A tree stump is pulled northward by a 10-N force at the same time a 25-N force pulls it southward. The resultant force has a magnitude of A) 0 N. B) 15 N. C) 25 N. D) 150 N.

Q: A block pulled to the left with 15 N and to the right with 5 N at the same time experiences a net force of A) 5 N. B) 10 N. C) 15 N. D) 20 N.