Exam 1

Select the correct equations that show that the acceleration of a hamster is 5 m/s^2 when it increases its velocity from rest to 10 m/s in 2 s. (A) a = Δv/t =(10m/s)/(2s) = 5m/s^2 (B) a = Δv⋅t = (10m/s)⋅(2s) = 5m/s^2 (C) a = (Δv)^2/t = (10m/s)^2/(2s) = 5m/s^2 (D) a = Δv/t^2 = (10m/s)/(2s)^2 = 5m/s^2

(A) a = Δv/t =(10m/s)/(2s) = 5m/s^2

Three balls of different masses are thrown straight upward with initial speeds as indicated. (A) From fastest to slowest, rank the speeds of the balls 1 ss after being thrown. Rank the speeds of the balls from fastest to slowest. To rank items as equivalent, overlap them. (B) From greatest to least, rank the accelerations of the balls 1 ss after being thrown. Or are the accelerations the same? Rank accelerations of the balls from greatest to least. To rank items as equivalent, overlap them.

(A) fastest to slowest C A B (B) Greatest to Least A,B,C (All the same)

Since an object weighs less on the surface of the Moon than on Earth's surface, does it have less inertia on the Moon's surface? (A) Yes (B) No

(B) No

How does the force of friction for a sliding object vary with speed? (A) The force of friction is zero for a sliding object. (B) The force of friction is approximately independent of speed. (C) The force of friction is inversely proportional to speed. (D) The force of friction is proportional to speed.

(B) The force of friction is approximately independent of speed

If the system is considered to be the apple and the orange together (Figure 1), is there a net force on the system when the apple pulls (ignoring friction with the floor)? (A) There is no net force because the system is frictionless. (B) The net force is zero because the action and reaction forces are equal and opposite. (C) Yes, there is a net force because the orange must accelerate when pulled. (D) Yes, the action of the apple is on the orange, so the net force is not zero.

(B) The net force is zero because the action and reaction forces are equal and opposite

When you stand at rest on a bathroom scale, how does your weight compare with the support force from the scale? (A) Your weight is equal in magnitude and in the same direction as the support force from the scale. (B) Your weight is equal in magnitude and opposite in direction to the support force from the scale. (C) The support force from the scale is half your weight. (D) The support force from the scale is twice your weight.

(B) Your weight is equal in magnitude and opposite in direction to the support force from the scale

Cassy can get more force on the bricks she breaks with a blow of her bare hand when _______. (A) does so with great determination. (B) her hand is made to bounce from the bricks. (C) she exerts follow-through (D) she toughens her hand beforehand

(B) her hand is made to bounce from the bricks

A vertical vector of 3 units combined with a horizontal vector of 4 units has a resultant of (A) 7 units. (B) 1 unit. (C) 5 units.

(C) 5 units

How does acceleration depend on the net force? (A) Acceleration is inversely proportional to the net force. (B) Acceleration is independent of the net force. (C) Acceleration is proportional to the net force. (D) Acceleration is equal to the net force.

(C) Acceleration is proportional to the net force

What is the net force on a bag pulled down by gravity with a force of 18 newtons and pulled upward by a rope with a force of 18 newtons? (A) The net force is 36 newtons. (B) The net force is 25 newtons. (C) The net force is zero newtons. (D) The net force is 18 newtons.

(C) The net force is zero newtons

A pair of action-reaction forces always (A) act on the same object. (B) comprise a pair of interactions. (C) occur simultaneously. (D) all of the above (E) none of the above

(C) occur simultaneously

When hitting a tennis ball with your racquet, the force on the ball has the same magnitude as the force on the _______. (A) hand that holds the racquet (B) player (C) racquet (D) racquet, and in the same direction

(C) racquet

Why do we say that force is a vector quantity? (A) A force has a magnitude, but not a direction. (B) A force is measured in pounds, and pounds are a vector quantity. (C) A force is a scalar quantity. (D) A force has a magnitude and a direction.

(D) A force has a magnitude and a direction

What two units of measurement are necessary for describing speed? (A) Average speed and time (B) Average speed and distance (C) Distance and length (D) Distance and time

(D) Distance and time

What relationship between the Sun and Earth did Copernicus formulate? (A) The Sun revolved in a circle about the Earth. (B) The Sun and the Earth revolve in circles around each other. (C) The Earth was at rest with respect to the Sun. (D) The Earth revolved in a circle about the Sun.

(D) The Earth revolved in a circle about the Sun

What is the net force acting on a 1-kg ball in free fall? Express your answer with the appropriate units.

10.0 N

What is the net force acting on a falling 1-kg ball if it encounters 2 N of air resistance? Express your answer with the appropriate units.

7.80 N

A track is made of a piece of channel iron bent as shown. A ball released at the left end of the track continues past the various points. Rank the speed of the ball at points A, B, C, and D, from fastest to slowest. Watch for tie scores. Rank from fastest to slowest. To rank items as equivalent, overlap them.

Fastest to Slowest: C B,D A

A different scaffold that weighs 400 N supports two painters, one 500 N and the other 400 N. The reading in the left scale is 800 N. What is the reading in the right-hand scale? Express your answer to two significant figures and include the appropriate units.

T = 500 N

Part A Before you click "Play," predict what will happen if the red and green truck with equal mass and equal magnitude of velocity collide. (A) The trucks will stick together after the collision and move to the left. (B) The trucks will stick together after the collision and move to the right. (C) The trucks will stick together after the collision and not move. Part B Predict what will happen if you reduce the magnitude of the velocity of the green truck to a magnitude smaller than that of the red truck. (A) The trucks will stick together after the collision and move to the right. (B) The trucks will stick together after the collision and move to the left. (C) The trucks will stick together after the collision and not move. Part C Click "Reset." Now, predict what will happen if you change the velocity of the red truck so that it has a magnitude smaller than that of the green truck but is negative. (A) The trucks will stick together after the collision and not move. (B) The trucks will stick together after the collision and move to the left. (C) The trucks will stick together after the collision and move to the right. Part D Click "Reset." Now, predict what will happen if you change the velocity of the red truck so that it has a magnitude smaller than that of the green truck but is positive. (A) The trucks will stick together after the collision and move to the left. (B) The trucks will stick together after the collision and move to the right. (C) The trucks will stick together after the collision and not move. Part E Click "Reset." Now, predict what will happen if you increase the mass of the green truck so that it is greater than the mass of the red truck. (A) The trucks will stick together after the collision and not move. (B) The trucks will stick together after the collision and move to the right. (C) The trucks will stick together after the collision and move to the left.

Part A (C) The trucks will stick together after the collision and not move Part B (B) The trucks will stick together after the collision and move to the left Part C (C) The trucks will stick together after the collision and move to the right Part D (B) The trucks will stick together after the collision and move to the right Part E (B) The trucks will stick together after the collision and move to the right

A force of gravity pulls downward on a book on a table. What force prevents the book from accelerating downward? Enter the name of the force only.

normal force

Surprisingly, very few athletes can jump more than 2 feet (0.6 m) straight up. Use d = 1/2gt^2 and solve for the time one spends moving upward in a 0.6-m vertical jump. Then double it for the "hang time"-the time one's feet are off the ground. Express your answer to two significant figures and include the appropriate units.

t = 0.70 s

In daily life, we see many cases of people who are caught misrepresenting things and who soon thereafter are excused and accepted by their contemporaries. How is this different in science? (A) A scientist who lies in a scientific publication will suffer professional excommunication. (B) A scientist who proposes a hypothesis that is eventually disproven is never allowed to be a scientist again. (C) A scientist who makes a mistake is never allowed to be a scientist again. (D) A scientist who disagrees with current theory is never allowed to be a scientist again.

(A) A scientist who lies in a scientific publication will suffer professional excommunication

Why is physics considered to be the basic science? (A) Because all other sciences can be shown to be derived from it. (B) As physicist Paul Tipler says about sciences other than physics, "What other sciences?" (C) Physics involves matter that is alive. (D) Physics is about how atoms combine to form molecules.

(A) Because all other sciences can be shown to be derived from it

What are the units for force? (A) Force can be expressed in newtons or pounds. (B) Force must be measured in newtons; it can never be measured in pounds. (C) Force must be measured in pounds and then converted to newtons. (D) Force must first be measured in newtons, then converted to pounds.

(A) Force can be expressed in newtons or pounds

What did Galileo discover in his legendary experiment on the Leaning Tower of Pisa? (A) Galileo found that a heavier stone does not fall significantly faster than a lighter one. (B) Galileo found that stones fall faster proportional to their weight. (C) Galileo found that a heavier stone falls significantly faster than a lighter one. (D) Galileo found that air resistance significantly slowed falling stones.

(A) Galileo found that a heavier stone does not fall significantly faster than a lighter one

State the equilibrium rule for forces in symbolic notation (A) ΣF = 0 (B) ΣF = 2 mg (C) ΣF = net force (D) ΣF = -mg

(A) ΣF = 0

What kind of speed is registered by an automobile speedometer? (A) Minimum speed (B) Maximum speed (C) Instantaneous speed (D) Average speed

(C) Instantaneous speed

Weight = mg Calculate the weight in newtons of a 1900-kg elephant. Express your answer to two significant figures and include the appropriate units.

W = 1.9 x 10^4 N

A hungry fish is about to have lunch at the speeds shown. Assume the hungry fish has a mass 5 times that of the small fish. Immediately after lunch, for each case, rank from greatest to least the speed of the formerly hungry fish. Rank from greatest to least. To rank items as equivalent, overlap them.

greatest to least C A B

Impulse = Ft What impulse occurs when an average force of 5.0 N is exerted on a cart for 2.5 s? Express your answer to two significant figures and include the appropriate units.

p = 13 (kg x m)/s

Momentum = mv What is the momentum of an 7.8-kg bowling ball rolling at 1.0 m/s? Express your answer to two significant figures and include the appropriate units.

p = 7.8 (kg x m)/s

Boxes of various masses are on a friction-free, level table. (A) From greatest to least, rank the net forces on the boxes. Rank from greatest to least. To rank items as equivalent, overlap them. (B) From greatest to least, rank the accelerations of the boxes. Rank from greatest to least. To rank items as equivalent, overlap them.

(A) Greatest to Least D C B A (B) Greatest to Least C B D A

Why are students of the arts encouraged to learn about science and science students encouraged to learn about the arts? (A) Knowing both the arts and sciences makes for a wholeness in the way we view the world. (B) Scientists need to learn how to write and writers need to learn what is impossible to do according to science. (C) Scientists need to relax by viewing art and artists need the discipline of learning science. (D) Scientists need to learn to draw and artists need to learn how to solve equations.

(A) Knowing both the arts and sciences makes for a wholeness in the way we view the world

According to the parallelogram rule, what quantity is represented by the diagonal of a constructed parallelogram? (A) The diagonal is the resultant, or sum, of two vectors. (B) The diagonal is the difference of two vectors. (C) The diagonal is always 1.41 times the magnitude of the sum of the vectors. (D) The diagonal is 1.41 times the magnitude of the longest vector.

(A) The diagonal is the resultant, or sum, of two vectors

Which is more likely to break: a hammock stretched tightly between a pair of trees or one that sags more when you sit on it? (A) The hammock stretched tightly between a pair of trees is more likely to break. (B) Both hammocks are equally likely to break. (C) The hammock that sags more when you sit on it is more likely to break.

(A) The hammock stretched tightly between a pair of trees is more likely to break

A ball is tossed with enough speed straight up so that it is in the air several seconds. Assume upward direction is positive and downward is negative. (A) What is the velocity of the ball when it reaches its highest point? Express your answer with the appropriate units. (B) What is its velocity 1 s before it reaches its highest point? Express your answer with the appropriate units. (C) What is the change in its velocity during this 1-s interval? Express your answer with the appropriate units. (D) What is its velocity 1 s after it reaches its highest point? Express your answer with the appropriate units. (E) What is the change in velocity during this 1-s interval? Express your answer with the appropriate units. (F) What is the change in velocity during the 2-s interval? (Careful!) Express your answer with the appropriate units. (G) What is the acceleration of the ball during any of these time intervals? Express your answer with the appropriate units. (H) What is the acceleration of the ball at the moment the ball has zero velocity? Express your answer with the appropriate units.

(A) v = 0 m/s (B) v = 10.0 m/s (C) Δv = -10.0 m/s (D) v = -10.0 m/s (E) Δv = -10.0 m/s (F) Δv = -20.0 m/s (G) a = -10.0 m/s^2 (H) a = -10.0 m/s^2

Select the correct equations that show that the average speed of a rabbit that runs a distance of 36 m in a time of 3 s is 12 m/s. (A) v = s/t = (36m)/(3s) = 12m/s (B) v = s^2/t = (36m)^2/(3s) = 12m/s (C) v = s/t^2 = (36m)/(3s)^2 = 12m/s (D) v = s x t = (36m) x (3s) = 12m/s

(A) v = s/t = (36m)/(3s) = 12m/s

Which of the following are scientific hypotheses? (A) Earth rotates about its axis because living things need an alternation of light and darkness. (B) Chlorophyll makes grass green. (C) Tides are caused by the Moon.

(B) Chlorophyll makes grass green (C) Tides are caused by the Moon

Impulse = change in momentum: Ft=Δmv How much impulse stops a 52-kg carton sliding at 4.2 m/s when it meets a rough surface? Express your answer to two significant figures and include the appropriate units.

J = 220 N x s

Lucy Lightfoot stands with one foot on one bathroom scale and her other foot on a second bathroom scale. Each scale reads 360 N. What is Lucy's weight? Express your answer with the appropriate units.

W = 720 N

When the Sun was directly overhead in Syene, why wasn't it directly overhead in Alexandria? (A) Gravity bends light. (B) Syene is in a different time zone than Alexandria. (C) The Earth is a sphere. (D) The Sun is a sphere.

(C) The Earth is a sphere

Consider a 100-kg box of tools in the locations A, B, and C. (A) From greatest to least, rank the masses of the 100-kg box of tools. Rank from greatest to least. To rank items as equivalent, overlap them. (B) From greatest to least, rank the weights of the 100-kg box of tools. Rank from greatest to least. To rank items as equivalent, overlap them.

(A) Greatest to Least A,B,C (B) Greatest to Least C A B

Which is normally greater: static friction or sliding friction on the same object? (A) Static friction is normally greater than dynamic friction. (B) Dynamic friction is normally greater than static friction. (C) On the same object, static friction and dynamic friction are equal. (D) Static friction and dynamic friction are both zero.

(A) Static friction is normally greater than dynamic friction

If the mass of a sliding block is tripled while a constant net force is applied, by how much does the acceleration change? (A) The acceleration is reduced to 1/3 of its original value. (B) The acceleration triples. (C) The acceleration is zero. (D) The acceleration remains the same.

(A) The acceleration is reduced to 1/3 of its original value

If you push on a crate with a horizontal force of 100 N and it slides at constant velocity, what is the magnitude and direction of the frictional force acting on the crate? (A) The frictional force on the crate is 100 N opposite the direction of motion. (B) The frictional force has nothing to do with you pushing on the crate. (C) The frictional force on the crate is 100 N in the same direction as the direction of motion. (D) The frictional force on the crate is zero newtons.

(A) The frictional force on the crate is 100 N opposite the direction of motion

In daily life, people are often praised for maintaining some particular point of view, for the "courage of their convictions." A change of mind is seen as a sign of weakness. How is this different in science? (A) When a scientist finds evidence that contradicts a law, then the law must be abandoned. (B) Once a scientific law is discovered, it never changes, so you must change your mind to believe it. (C) Scientific laws are decided to be true by majority vote. (D) When a famous scientist restates a law, then the old law must be abandoned.

(A) When a scientist finds evidence that contradicts a law, then the law must be abandoned

Acceleration is generally defined as the time rate of change of velocity. When can it be defined as the time rate of change of speed? (A) When moving in a straight line, the time rate of change of speed is acceleration. (B) When moving in a circle, the time rate of change of speed is always zero. (C) When moving in a straight line, the time rate of change of speed is called velocity. (D) When moving in a circle, the time rate of change of speed is called average speed.

(A) When moving in a straight line, the time rate of change of speed is acceleration

To produce an acceleration to a system there (A) must be a net force on the system. (B) must be acceleration outside the system also. (C) may or may not be a net force on the system.

(A) must be a net force on the system

Select the correct equations that show that a freely falling rock drops a distance of 45 m when it falls from rest for 3 s. (A) s = g⋅t^2/2 = (10m/s^2)⋅(3s)^2/2 = 45m (B) s = g⋅t/2 = (10m/s^2)⋅(3s)/2 = 45m (C) s = g^2⋅t/2 = (10m/s^2)^2⋅(3s)/2 = 45m (D) s = t^2/(2⋅g) = (3s)^2/(2⋅(10m/s^2)) = 45m

(A) s = g⋅t^2/2 = (10m/s^2)⋅(3s)^2/2 = 45m

When two vehicles collide, momentum is conserved _______. (A) whether the collision is elastic or inelastic. (B) if the collision is elastic (C) only if deformation of either vehicle does not occur. (D) if the collision is inelastic.

(A) whether the collision is elastic or inelastic

What is the acceleration of a car that maintains a constant velocity of 100 km/h for 10 s? (A) 1 km/h · s (B) 0 km/h · s (C) 0.1 km/h · s (D) 10 km/h · s

(B) 0 km/h · s

What is the role of equations in this book? (A) Equations will be derived to make you understand science. (B) Equations are guides to thinking and show connections between concepts. (C) Equations are interesting side notes about scientific concepts. (D) Equations are for plug-and-chug calculations.

(B) Equations are guides to thinking and show connections between concepts

In the apple-pulling-the orange sequence in this chapter, what is the force that accelerates the system across the floor? (A) The resistance to motion by the orange (B) Friction between the apple and the floor. (C) The backward pull by the orange (D) Internal forces.

(B) Friction between the apple and the floor

What did Galileo discover about moving bodies and force in his experiments with inclined planes? (A) Bodies rolling down a steep inclined plane starting at a given height rolled up a gently inclined plane to a higher height. (B) In the absence of a retarding force, a body will keep moving at a constant speed in a straight line forever. (C) Bodies rolling up an inclined plane sped up. (D) Bodies rolling down an inclined plane slowed down.

(B) In the absence of a retarding force, a body will keep moving at a constant speed in a straight line forever

What type of path does a moving object follow in the absence of a force? (A) It follows a circular path in the absence of a force. (B) It continues to move in a straight line at a constant speed. (C) It moves in a straight line and eventually slows to a stop. (D) It follows a parabolic trajectory in the absence of a force.

(B) It continues to move in a straight line at a constant speed

In which is momentum conserved: an elastic collision or an inelastic collision? (A) Momentum is conserved in neither elastic nor inelastic collisions. (B) Momentum is conserved in elastic and inelastic collisions. (C) Momentum is conserved only in elastic collisions. (D) Momentum is conserved only in inelastic collisions.

(B) Momentum is conserved in elastic and inelastic collisions

Must people choose between science and religion? (A) Yes, religion and science are completely antithetical. (B) No, religion and science are essentially the same. (C) No, there is no contradiction in being scientific and religious in one's thinking. (D) No, scientific and religious beliefs are incompatible.

(C) No, there is no contradiction in being scientific and religious in one's thinking

If the forces that act on a cannonball and the recoiling cannon from which it is fired are equal in magnitude, why do the cannonball and cannon have very different accelerations? (A) The cannon pushes on the cannon ball with a much greater force than the cannon ball pushes on the cannon. (B) The force from the cannon ball on the cannon produces little acceleration because it lasts for such a brief time. (C) Remember F = ma, and note that the cannon has a much greater mass than the cannon ball, so the cannon accelerates less for the same force. (D) The cannon weighs so much that friction with the ground alone prevents it from accelerating.

(C) Remember F = ma, and note that the cannon has a much greater mass than the cannon ball, so the cannon accelerates less for the same force

Shake something to and fro and you're measuring its what? Lift it against gravity and you're measuring its what? (A) Shaking measures neither mass nor weight. Lifting measures weight. (B) Shaking measures weight, whereas lifting measures mass. (C) Shaking measures mass, whereas lifting measures weight. (D) Shaking and lifting both measure weight.

(C) Shaking measures mass, whereas lifting measures weight

A boxer can hit a heavy bag with great force. Why can't he hit a piece of tissue paper in midair with the same amount of force? (A) The low-mass tissue exerts a smaller reaction force on the boxer than the action force the boxer exerts on the tissue. (B) The low-mass tissue floating in the air exerts no reaction force on the boxer. (C) The boxer can only hit the tissue paper with a force as large as the tissue paper can exert on the boxer, and the low-mass tissue can only exert a weak force. (D) The tissue paper can only exert a force on the boxer as large as the air resistance force exerts on the paper.

(C) The boxer can only hit the tissue paper with a force as large as the tissue paper can exert on the boxer, and the low-mass tissue can only exert a weak force

What two principal factors affect the force of air resistance on a falling object? (A) The force depends mostly on mass and speed. (B) The force depends mostly on mass and frontal area. (C) The force depends mostly on frontal area and speed. (D) The force depends mostly on g and mass.

(C) The force depends mostly on frontal area and speed

What is the net force on a cart that is pulled to the right with 100 pounds of force and to the left with 30 pounds of force? (A) The net force is zero. (B) The net force is 130 pounds. (C) The net force is 70 pounds to the right. (D) The net force is 70 pounds to the left.

(C) The net force is 70 pounds to the right

What is the net force on an object in either static or dynamic equilibrium? (A) The net force is zero for static equilibrium and greater than zero for dynamic equilibrium. (B) The net force is vertical for static equilibrium and horizontal for dynamic equilibrium. (C) The net force is zero. (D) The net force is equal and opposite to the weight of the object.

(C) The net force is zero

Why doesn't a heavy object accelerate more than a light object when both are freely falling? (A) The inertia of the heavy object equals the inertia of the lighter object, so their accelerations are the same. (B) The larger air resistance force on the larger object makes it fall with the same acceleration. (C) The ratio of the weight to mass is the same for all objects in the same locality. (D) The inertia of the heavy object is just enough smaller than the inertia of the lighter object to counteract the larger gravity force.

(C) The ratio of the weight to mass is the same for all objects in the same locality

The quantity that is called impulse can be measured by the _______. (A) how long the force acts compared to the amount of time (B) difference between force and time. (C) product of force and time. (D) addition of force and time.

(C) product of force and time

What is the test for whether a hypothesis is scientific or not? (A) A hypothesis is scientific if it is possible to prove it right. (B) A hypothesis is scientific if the appropriate scientific body says it is. (C) A hypothesis is scientific if it can be written as an equation. (D) A hypothesis is scientific if it is possible to prove it wrong.

(D) A hypothesis is scientific if it is possible to prove it wrong

What exactly is meant by a "freely falling" object? (A) An object in free fall falls with constant speed. (B) An object in free fall falls with constant velocity. (C) An object in free fall falls under gravity in air with air resistance but no other resistance. (D) An object in free fall falls under gravity alone with no friction.

(D) An object in free fall falls under gravity alone with no friction

What does it mean to say something is in mechanical equilibrium? (A) An object in mechanical equilibrium is always in motion. (B) An object in mechanical equilibrium must experience no forces. (C) An object in mechanical equilibrium experiences a net force twice its weight. (D) An object in mechanical equilibrium experiences a zero net force.

(D) An object in mechanical equilibrium experiences a zero net force

What relationship between distance traveled and time did Galileo discover for freely falling objects released from rest? (A) Galileo discovered that distance was independent of time. (B) Galileo discovered that distance increased inversely proportional to time. (C) Galileo discovered that distance increased proportional to time. (D) Galileo discovered that distance increased as the time squared.

(D) Galileo discovered that distance increased as the time squared

What are steps of the scientific method. (A) Using Occam's razor to eliminate excess facts. (B) Reasoning and derivation from axioms. (C) Assembling and organizing facts and checking them against dogma. (D) Hypothesis, predictions, and experimental findings.

(D) Hypothesis, predictions, and experimental findings

Consider the system of a single football. If you kick it, is there a net force to accelerate the system? If a friend kicks it at the same time with an equal and opposite force, is there a net force to accelerate the system? (A) If you kick the football, or if you and your friend kick it, in both cases, there is a net force to accelerate the system. (B) If you kick the football, there is no net force to accelerate the system due to the force applied by the football on you. If you and your friend kick the football, there is a net force. (C) If you kick the football, there is no net force to accelerate the system due to the force applied by the football on you. The same thing applies if you and your friend kick the ball. (D) If you kick the football, there is a net force to accelerate the system; if you and your friend kick it, there is not.

(D) If you kick the football, there is a net force to accelerate the system; if you and your friend kick it, there is not

Fill in the blanks: Newton's first law is often called the law of _______. Newton's second law is the law of _______. and Newton's third law is the law of _______. (A) Acceleration, inertia, action -reaction (B) Inertia, net force, friction (C) Action, inertia, force (D) Inertia, acceleration, action -reaction

(D) Inertia, acceleration, action -reaction

What is the distance fallen for a freely falling object 1 s after being dropped from a rest position? What is the distance for a 4-s drop? (A) It falls 5 m in 1 s and 5 m in 4 s. (B) It falls 10 m in 1 s and 160 m in 4 s. (C) It falls 5 m in 1 s and 20 m in 4 s. (D) It falls 5 m in 1 s and 80 m in 4 s.

(D) It falls 5 m in 1 s and 80 m in 4 s

If a car is moving at 90 km/h and it rounds a corner, also at 90 km/h, does it maintain a constant speed? A constant velocity? (A) It maintains a constant velocity, but not a constant speed. (B) It does not maintain a constant speed or a constant velocity. (C) It maintains a constant speed and a constant velocity. (D) It maintains a constant speed, but does not maintain a constant velocity.

(D) It maintains a constant speed, but does not maintain a constant velocity

Consider hitting a baseball with a bat. If we call the force on the bat against the ball the action force, identify the reaction force. (A) The reaction force is the force of the bat on the ball. (B) The reaction force is the force due to compression inside the ball. (C) The reaction force is zero because the force of the bat on the ball is equal and opposite to the force of the ball on the bat. (D) The reaction force is the force by the ball on the bat.

(D) The reaction force is the force by the ball on the bat

As you read this in your chair, how fast are you moving relative to the chair? Relative to the Sun? (A) You are moving over 100,000 km/h relative to the chair and the Sun. (B) You are not moving relative to the chair, and you are not moving relative to the Sun. (C) You are stationary relative to the Sun, but you are moving relative to the chair. (D) You are not moving relative to the chair, but you are moving over 100,000 km/h relative to the Sun.

(D) You are not moving relative to the chair, but you are moving over 100,000 km/h relative to the Sun

Once the crate is sliding, how hard do you push to keep it moving at constant velocity? (A) You push with a force slightly greater than the static friction force. (B) You no longer need to push once the crate is sliding. (C) You push with a force slightly greater than the dynamic friction force. (D) You push with a force equal to and opposite the dynamic friction force.

(D) You push with a force equal to and opposite the dynamic friction force

When a ball falls downward, it may have a net force (A) equal to its weight minus air drag. (B) of zero. (C) equal to its weight. (D) any of the above (E) none of the above

(D) any of the above

When a big fish swims into an oncoming smaller fish and swallows it, the momentum of the two-fish system _______. (A) increases. (B) decreases. (C) converts to spurious motion. (D) remains the same.

(D) remains the same

Suppose that a freely falling object were somehow equipped with a speedometer. By how much would its reading in speed increase with each second of fall?

Its speed reading would increase by 10 m/s each second.

You are driving north on a highway. Then, without changing speed, you round a curve and drive east. Does your velocity change? Do you accelerate? Explain.

Yes your velocity changes, and yes you accelerate.

Acceleration: a = F(net)/m Calculate the acceleration of a 300000-kg jumbo jet just before takeoff when the thrust on the aircraft is 120000 N. Express your answer to two significant figures and include the appropriate units.

a = 0.40 m/s^2