AP Physics 2 Final Review (AP CLASSROOM QUIZZES)
Two point charges with charges Q1=+2μC and Q2=−4μC are located on the horizontal axis, as shown in the figure. The distance between their centers is 1.0m. Point P is midway between the point charges. Which of the following is the best visual representation of the electric field vectors from both Q1 and Q2 at point P?
--------> ------------------>
The graph shows the electric potential along the x−x−axis in a region of space. What is the magnitude of the average electric field between x=2m and x=4m?
30 V/m
The following data are obtained from various sources and investigations. Based on these data, which of the following represents the order of the substance densities ranked from greatest density to least density?
Gold, silver, copper, iron
A charged rod is placed near a grounded conducting sphere. The rod is moved away, and then the ground is removed. What is the resulting charge, if any, on the sphere after the process is complete?
No net charge
A student has four pieces of a substance in different shapes and sizes. The student wants to determine the density of the substance. Which of the following procedures would yield the most accurate data?
Place the pieces on a mass balance, one at a time and record the mass of each. Submerge the pieces one at a time in a graduated cylinder filled with a volume of water and record the volume change.
A student wants to determine the change in the density of a liquid as a function of its temperature. The student has various measuring devices and some blocks that will float in the liquid. The upward force exerted on the objects by the liquid is equal to the product of the density of the liquid, the volume of the block that is underwater, and the acceleration due to gravity. Which of the following is an appropriate experimental method? Select two answers.
Put a known mass of the liquid in a container with a known cross-sectional area. Record the depth of the liquid as the temperature is increased. Let a block of known mass and cross-sectional area float in the liquid. Record the height of the submerged part of the object as the temperature is increased.
Identical blocks 1 and 2 are placed into contact with each other. The temperature of block 1 is initially greater than the temperature of block 2. What quantity is transferred between the blocks and what is the direction of the transfer?
Quantity Transferred - Molecular kinetic energy Direction of Transfer - From block 1 to block 2
A jar contains vinegar and oil that have separated into layers, as shown in the figure. Which of the following correctly identifies a Newton's third law force pair?
The weight of the vinegar and the gravitational force of the vinegar on Earth
A puddle on the street has a layer of oil floating on it. Which of the following correctly identifies a Newton's-third-law force pair?
The weight of the water and the gravitational force exerted by the water on Earth
Three identical conducting spheres are arranged on insulating stands and equally spaced, as shown. Sphere 1 initially has a net charge of Q0 , while spheres 2 and 3 are initially uncharged. Sphere 1 is touched briefly to sphere 2 and moved away; then sphere 2 is touched briefly to sphere 3 and moved away. After the processes, in which direction, if any, is the net electric force exerted on sphere 2 ?
To the right
A 1.0L closed flask holds a fixed volume of gas with a total internal energy of 300J. Then 50J of energy is added to the gas by heating. What is the work WW done on the gas and the change ΔU in the total internal energy of the gas?
W=0J; ΔU=50J
A gas-filled balloon is moved from a warm room to a cold refrigerator. The gas contracts, so the balloon does work W on the gas and the gas loses thermal energy Q to its surroundings. Which of the following indicates and justifies the correct form of the first law of thermodynamics during this process?
ΔU=−Q+W, because thermal energy is transferred to the surroundings and work is done on the gas.
Spheres AA and BB are identical in size and made from the same conducting material. Sphere AA is attached to an insulating rod, and sphere BB is suspended from an insulating thread. Sphere AA initially has a charge of +10 nC+10 nC, and sphere BB is initially uncharged. Which of the following best represents the distribution of charge on the surfaces of spheres AA and BB when sphere AA is brought near sphere BB?
+ - + + - + + - + + - + + - +
Two particles, with charges of +1μC and −1μC, are placed at the opposite corners of a cube with edges of length 1cm, as shown in the figure. The magnitude of the electric force on a third particle with charge +1μC placed on the corner of the cube labeled PP is most nearly
100N
Particles are arranged at the vertices of two equilateral triangles, as shown in the figure. Each triangle has side length r, and each particle has a charge of magnitude q. What is the magnitude of the force on the particle with charge +q?
2kq^2/r^2
A sphere with charge q is fixed at the bottom left corner of the right triangle shown in the figure. Points P and R are at the locations shown. If the magnitude of the electric field due to the sphere at point P is EP, what is the magnitude of the field at point R, and why?
9EP / 100, because the electric field is inversely proportional to the square of the distance from the charge.
In an experiment, a cylinder of height 0.10m and cross-sectional area 0.004m^2 has a movable piston with negligible mass and contains an ideal gas. The gas is taken through cycle ABCA as its absolute pressure and volume are recorded. The graph shows the best-fit curves for the data. During which process was the most work done on the gas?
AB
Two containers of equal volume contain equal amounts of an ideal gas. The average speed of the molecules in container 1 is twice the average speed of the molecules in container 2. The two containers are then connected by a tube as shown. Which of the following correctly identifies the direction of heat flow and correctly describes the change in average speed of the molecules originally contained in container 2 ?
Direction of heat flow --> Speed of molecules in container 2 increases
Which of the following correctly compares the magnitude Fg of the gravitational force and the magnitude FE of the electrostatic force exerted between two electrons?
FE>Fg, because the product of the charge of an electron and the Coulomb's law constant k is greater in magnitude than the product of the mass of an electron and the universal gravitational constant G.
The figure shows metal spheres X and Y that are suspended by identical strings of negligible mass. The spheres have the same mass and charges as shown and are in equilibrium. A free-body diagram for each sphere is also shown. Which of the following are correct based on the free-body diagrams? Select two answers.
FGX=FGY TX=TY
A student has two identical uncharged metal spheres on insulating stands, sphere AA and sphere BB. The student also has a metal grounding wire and a negatively charged insulating rod. Which of the following describes a procedure that will result in spheres AA and BB having equal positive charge? Select two answers.
Hold the charged rod near one side of sphere AA and touch the other side of sphere AA with the wire. Then remove the rod and wire. Then touch sphere AA and sphere BB. Then separate the spheres. Hold the charged rod near one side of sphere AA and touch the other side of sphere AA with the wire. Then hold the charged rod to one side of sphere BB and touch the other side of sphere BB with the wire.
Two isolated particles, A and B, lie along the xx-axis. The particles have the same net charge +Q, but different masses with MA>MB. Is there a point along the x-axis where both the net electric field and net gravitational field of the particles are zero, and if so, in what region is the point?
No, there is no point on the x-axis where both the fields are zero.
Two point charges with charges Q1=+2μC and Q2=−4μC are located on the horizontal axis, as shown in the figure. The distance between their centers is 1.0m. Point P is midway between the point charges. Suppose we wish to represent the electric potential around Q1 and Q2 by drawing isolines. What is the relationship of the isolines of electric potential to the net electric field vectors in the region around Q1 and Q2?
The isolines are always perpendicular to the electric field vectors.
A container holds electrically charged gas particles at high temperature. Which of the following correctly describes the interactions between the particles?
The particles exert both electrical and gravitational forces on one another because they have both charge and mass.
An ideal gas is sealed in an insulated container with a movable piston. What happens to the temperature of the gas as it is compressed?
The temperature increases.
Two charged particles, X and Y, are fixed on a grid as shown in the figure. The particles have the same amount of charge but with opposite signs, as shown. Which of the following best represents the direction of the net electric field at point pp due to the two particles?
| | \/
Three objects are held along a line, as shown in the figure. Particle P with charge −q and mass mm is a distance dd from sphere A with charge −q. Sphere B with charge +2q is a distance dd on the other side of sphere A. The electric forces exerted on each of the objects is also shown, and gravitational forces are negligible. Particle P is then released. What is the magnitude of its acceleration immediately after release?
(FPA - FPB) / m
The figures show four small charged spheres of the same size and electric field vectors at the same distance from each sphere. Which of the following correctly ranks the magnitude of the charges Q on the spheres?
(QW=QX)>(QY=QZ)
The figure represents an uncharged balloon and an uncharged wall. When the balloon is brought near the wall, they do not exert any electrostatic force on each other. A person then rubs the balloon on a piece of cloth and observes that the balloon now sticks to the wall when brought near it. Based on this evidence, which of the following could model the excess charges in the balloon and the molecules near the surface of the wall when the balloon sticks to the wall? Select 2 Answers.
+- + -+ - +- + -+ - +- + -+ - +- + -+ - +- + -+ -
The figure shows a horizontal pipe with a circular cross section whose diameter varies. The cross-sectional area at X is 3.0×10−4m2 and at Y is 0.60×10−4m2. Water of density 1000kg/m31000kg/m3 fills the pipe and flows through it at a constant rate of 2.4×10−4m3/s. The difference in pressure between X and Y is most nearly
7700 Pa
Two identical, uncharged metal spheres are connected by a wire, as shown in the figure. Students who know nothing about induction are performing an experiment in which they bring a positively charged rod near the left side of the left sphere. As a result, electrons move to the vicinity of point PP . Near which of the other labeled points should the students place a charge detector to investigate where there is an excess of positive charge due to the motion of the electrons?
At all three points
In an experiment, rectangular solid objects of varying sizes made of the same material are floated in water. The data table gives the dimensions of each object and how much of that object is floating above the water. Which two of the following variables together can be used to calculate the density of the object? Select two answers.
Height above water Height
The figure shows four identical cubes at rest in a liquid. Which of the following is true about the claim that the force on the sides of cube DD is greater than the force on the sides of the other cubes?
It is correct, because the liquid molecules at that depth hit cube D with greater average force than the molecules that hit the other cubes.
A student has three objects of different shapes, as shown, and wants to compare their densities using liquids of known density. Which of the following experimental methods will allow the comparison to be made?
Let each object float in the same liquid, and compare the fractions of the objects' volumes that are below the liquid surface.
The left figure shows a small positively charged sphere and point P, located on the vertices of a triangle. In the right figure, a small negatively charged sphere is added at the third vertex. The charge on this sphere has the same magnitude as the positive charge on the other sphere. Which of the following correctly shows the direction of the electric field at P for the two situations?
One Sphere / Two Spheres -->
The figure shows a region of uniform electric field with magnitude 0.2N/C, represented by the vertical electric field vectors. The dashed horizontal lines represent lines of uniform electric potential. If the diagram represented the gravitational field near Earth's surface instead of an electric field, which of the following could be a correct description of the diagram?
The field lines point to the surface of Earth, and the dashed lines are lines of equal altitude.
A student claims that the force on the sides of a tall object submerged in water is the same at all points on the object. Which of the following is evidence that indicates the student is wrong?
The pressure of the water increases with depth, so molecules of water must, on average, exert a greater force on a surface at a greater depth.
Conducting spheres 1 and 2 are on insulated stands and are placed close to each other, as shown in the figure. The spheres are initially uncharged, and sphere 1 is connected to ground. A rod carrying positive charge is brought near the right side of sphere 2. The ground is disconnected and then the rod is removed. Which of the following represents the resulting charge distribution on the two spheres?
- + - - + - - + - - + - - + -
At the instant shown in Figure 1, a particle with charge −q−q is moving with speed vv in the +x+x -direction. An electric force is exerted on the particle in the +y+y -direction, as shown in the free-body diagram in Figure 2. In which direction is the acceleration of the particle?
/\ | | |
The figure shows an insulated bottle containing some hot coffee. The outer wall has a small hole in it so that air will fill the space between it and the inner wall. Which of the following describes the primary processes by which energy moves from the hot coffee to the outer wall of the container?
Conduction and convection
A sample of an ideal gas with initial volume VV is compressed isothermally until its volume is V2V2. Which of the following claims is correct about the transfer of energy by heating and the work done on the gas?
Energy Transferred by Heating - Out of the gas Work Done on the Gas - Positive
One mole of an ideal gas is sealed in a cylindrical container with a movable piston. The volume and pressure of the gas are recorded as the gas is taken through process ABCAABCA, as shown in the graph. Which of the following features of the graph, if any, is equivalent to the amount of work done on the gas during the complete cycle?
The area bound by the triangle ABCA
The figures show situations 1 and 2. In situation 1, a positively charged 0.10kg insulating sphere is suspended at rest 0.10m above a large positively charged metal plate. In situation 2, a positively charged 0.20kg insulating sphere is located 0.20m above the positively charged metal plate and is in motion. The magnitudes of the charges on the spheres are the same. Which of the following, if any, correctly describes a Newton's third law interacting force pair in situation 1?
The charged plate repelling sphere 1 and sphere 1 repelling the plate, because these forces are equal, opposite, and acting between the same two objects.
The buoyant force on a block submerged in salt water is greater than the buoyant force on the block when it is submerged in tap water. Which of the following describes the microscopic cause of this difference?
The electrostatic force between the electrons in the molecules in the block and the electrons in the molecules of the salt water is greater than the force between the electrons in the molecules in the block and the electrons in the molecules of the tap water.
A block is submerged in a container of fluid. Which of the following describes the microscopic cause of the force that the fluid exerts on the block?
The electrostatic force between the electrons in the molecules of the block and the electrons in the molecules of the fluid
A tank with a diameter of 10m is open at the top and contains water that is 12m deep. There is a hole 1.0m from the bottom of the tank with a diameter of 0.02m. The speed of the water as it exits the hole is most nearly
14.8m/s
Two identical spheres each have a charge of +3.0μC and are held at vertices of an equilateral triangle with sides of length 3m, as shown in the figure. Point P is at the third vertex of the triangle and 2.6m above the midpoint between the spheres. The magnitude of the electric field at point P is most nearly
5200N/C
A stone is accelerating downward through water. Which of the following describe a force that the water exerts on the stone? Select two answers.
A buoyant force directed upward A frictional force directed upward
A balloon is floating in air. Which of the following describes the microscopic cause of the downward force exerted on the air by the balloon?
Electrostatic repulsion between the electrons in the molecules in the air and the electrons in the molecules of the balloon
The figure shows three point charges with charges +q , −3q , and −5q located at the vertices of an equilateral triangle with side length a . Which of the following correctly characterizes the magnitude Fnet of the net electric force exerted on the positive charge?
Fnet < 1/4πε0 * 8q^2/a^2
An ideal gas is taken through an isobaric compression, as shown in the pressure-volume diagram. Which of the following claims is correct about the direction of the energy transfer, if any, between the gas and its surroundings during this process?
Heat energy is transferred from the gas to the surroundings.
A particle with a small electric charge is moved in an electric field by an external force. When the particle is moved along an electric potential isoline, in what direction, if any, is the force exerted by the electric field on the particle?
Perpendicular to the direction of the particle's motion
A charged particle of mass m is traveling horizontally with speed v0 when it enters the region between two horizontal, oppositely charged parallel plates. The particle follows the path indicated in the figure, hitting the bottom plate. Which of the following factors determine the time the particle takes to reach the bottom plate? Select two answers.
The mass of the particle The magnitude of the charge on each plate
Two particles with positive charges of q1 and q2, respectively, lie on the x-axis, with the particle of charge q1 at the origin and the other particle at x=d, as shown in the figure. The particle at the origin is held fixed in place, and the other particle is released and moves to the right. Which of the following graphs best represents the electric force exerted on the released particle as a function of position x?
| | | | | | | \ | \ -- ---------- _ _ _ _ _ _ _ _ ___ _ __ _ _ _ _
A student has three objects of the same material and shape but of different sizes, as shown, and wants to determine the density of the material. The student hangs each object on a scale and submerges each completely in a liquid so that three data points may be obtained. Which of the following steps is required to be sure that all three data points are valid?
Ensuring that none of the objects touch the bottom of the container that holds the liquid.
An insulated cylinder with a movable piston contains an ideal gas. The gas is allowed to expand freely, pushing the piston to the right, as shown in the figure. What happens to the internal energy of the gas as a result?
The internal energy decreases.
A pipe of radius RA carries water moving at a speed vA at point A. The pipe then narrows to a smaller radius RB and travels upward a distance H to point B, where the water is moving at speed vB. Which of the following is a correct expression for the pressure difference PA−PB between points A and B?
pgH+12p(v2B−v2A)
Two solid conducting spheres, sphere AA and sphere BB, are made of the same material. Sphere AA is smaller than sphere BB and initially has a charge of q0. Sphere BB is initially uncharged. The spheres are brought into contact and then separated and released from rest. When the spheres are released, sphere AA has charge qA and moves to the left with acceleration aA, while sphere BB has charge qB and moves to the right with acceleration aB. Which of the following correctly compares qA to qB and aA to aB? Assume gravitational effects are negligible.
qA<qBaA>aB
A gas is confined in a closed container with a movable piston. The container is kept in a hot water bath. Blocks of different known masses are placed on top of the piston one at a time, and the gas is allowed to come to equilibrium. The pressure and volume of the gas are recorded each time. The gas is taken from initial state I to final state F, which has a lower pressure. Which of the following correctly ranks the magnitudes of the work W done on the gas, the energy Q transferred to the gas by heating, and the change in internal energy ΔU of the gas?
(W=Q)>ΔU
A liquid at rest in a fixed container exerts a force perpendicular to the wall of the container. Two students make claims about the microscopic cause of this force. Student AA says that the force exerted by individual molecules as they bounce off the wall is always perpendicular to the wall. Student BB says that the molecules may strike the wall at angles that are not perpendicular. Which student is correct and why?
. The molecules in a liquid are in random motion at the microscopic scale. For every atom that hits at an angle to one side of perpendicular, there is likely to be another atom hitting at the same speed at the same angle on the other side of perpendicular. On average the nonperpendicular components cancel.
The figures show situations 1 and 2. In situation 1, a positively charged 0.10kg insulating sphere is suspended at rest 0.10m above a large positively charged metal plate. In situation 2, a positively charged 0.20kg insulating sphere is located 0.20m above the positively charged metal plate and is in motion. The magnitudes of the charges on the spheres are the same.
/\FE /\ FE | | | | * * | | | | \/FG | | \/ FG
A gas is confined in a closed container with a movable piston. The container is kept in a hot water bath. Blocks of different known masses are placed on top of the piston one at a time, and the gas is allowed to come to equilibrium. The pressure and volume of the gas are recorded each time. When a 200g block is placed on the piston, the volume of the gas goes from 5×10^−5m^3 to 4.7×10^−5m^3, while the pressure goes from 5.4×10^4Pa to 5.7×10^4Pa. If the surface area of the piston is 1×10^−3m^2 , the energy transferred to the gas due to the compression is most nearly
0.006 J
A triangular wedge is attached to a vertical wall. A hose directs a horizontal stream of water at the wedge, as shown. The stream of water is deflected vertically up and down after striking the wedge. The wedge and wall do not move. If the net force exerted on the water by the wedge is 1000N to the left, what is the net force exerted on the wedge by the water?
1000 N to the right
An ideal gas is taken through cycle ABCA, shown in the figure above, where process CA is isothermal. What is the work done by the gas on its surroundings during process ABC?
10kJ
A point charge of −q is located at (x,0)(x,0), and a point charge of +q is located at (−x,0), as shown. What are the magnitude and direction of the electric field created by these point charges at the point (0,y), which is a distance r from each point charge?
2(q / 4πε0 * x / r^3), positive x−direction
A sealed cylinder with a movable piston contains N molecules of an ideal gas. The gas is initially in the state with pressure P0 and volume 3V0 shown on the graph of pressure P as a function of volume V. The gas is then taken through the two processes shown. How much energy is exchanged between the system and its surroundings by heating as the gas is taken through the two processes, and is the energy added to or removed from the gas?
2P0V0 removed
The figure shows a region of uniform electric field with magnitude 0.2N/C, represented by the vertical electric field vectors. The dashed horizontal lines represent lines of uniform electric potential. What would be the magnitude and direction of the force exerted on an electron by the electric field?
3.2×10^−20 N, directed upward
In a certain region of space, there is an electric potential difference of 120V between two points that are 0.25m apart. What is the magnitude of the average electric field in between the two points?
480 N/C
An engineer is designing a device to measure how the density of seawater changes with depth. The device consists of a hollow spherical metal container of known mass and volume that can hold weights of known mass. The weights can be added or removed without changing the volume of the device. The seawater exerts an upward buoyant force on the device given by Fb=ρVg, where ρ is the seawater's density, V is the volume of the device and g is the acceleration due to gravity. Which of the following correctly explains how the device could be used to measure the density of seawater at a particular depth?
Add or remove weights until the device remains at rest in equilibrium, and use the known mass and volume of the device to calculate the density of the seawater.
Students have a sample of an unusual fluid. The density ρf of the fluid varies with temperature to a much larger degree than most fluids. To investigate the relationship between the fluid's density and its temperature, a wooden cube is allowed to float in the fluid. The temperature of the fluid is varied and the unsubmerged volume VU of the cube is measured. The upward force exerted on an object by a fluid is equal to the product of the density of the fluid, the volume of the object that is submerged, and the acceleration due to gravity (F=ρVg). Which of the following must also be known to determine the density of the fluid at various temperatures?
Both the mass mm of the cube and the total volume V of the cube, because the equation mg=ρf(V−VU) can then be used
A block with twice the density of water is at rest on the bottom of a container partially filled with water, as shown in the figure. The normal force exerted by the bottom of the container on the block is FN . Which of the following correctly indicates the magnitude of the normal force exerted by the block on the container and provides a valid explanation?
Equal to FN, because the forces between the block and the container are an interacting force pair described by Newton's third law.
The figure shows two point charges, one positive and one negative, separated by a distance r. The magnitude of the charge on each point charge is q. If the initial force between the point charges is F0, what will the magnitude of the force between them be if the separation distance is increased to 3r and the magnitude of each charge is increased to 3q? Ignore gravitational effects.
F0
Negatively charged object A is attached to an uncharged wall made of insulating material. Negatively charged object B is connected to the wall by an insulating string. When object B comes to rest, it is displaced an angle θ from the wall, as shown. A free-body diagram for object B is also shown, with the magnitudes of the forces labeled. Which of the following is correct for the forces on object B?
FE=Tsinθ, mg=Tcosθ
Figure 1 shows two identical positive point charges of magnitude Q at two of the corners of an equilateral triangle of side length a. Figure 2 shows three identical positive point charges also of magnitude Q at the three corners of an equilateral triangle of side length a. Which of the following best represents the relative magnitude and direction of the electric field at point P in each figure?
Figure 1 \ \ Figure 2 |
The pressure that a liquid exerts on the bottom surface of a container is the net result of individual molecules in the liquid that collide with the surface. Which of the following correctly indicates and justifies the relationship between the force exerted on the surface by a molecule and the force exerted on a molecule by the surface during a single one of these collisions?
Fmoleculeonsurface=Fsurfaceonmolecule, because the force the molecule exerts on the surface is equal and opposite to the force the surface exerts on the molecule
In an experiment, an electroscope is uncharged, so its leaves are initially together. Another electroscope has a charge of unknown sign, so its leaves are initially separated. A glass rod is rubbed with silk, and another glass rod is rubbed with wool. Next, a rubber rod is rubbed with silk, and another rubber rod is rubbed with wool. The rods are then brought close to, but do not touch, the two different electroscopes. The results of this experiment are shown in the table. Which of the following are correct conclusions about the effects of rubbing the materials? Select two answers.
Glass rubbed with silk and rubber rubbed with wool both become charged. Glass rubbed with silk and rubber rubbed with wool have charges of opposite signs.
One end of a hose is connected to an elevated water tank and the other end is capped, as shown in the figure. The normal force exerted on the hose by the ground has magnitude FN. Then, a small hole is cut into the hose, causing water to spray upward. Which of the following correctly describes the magnitude of the normal force exerted by the ground on the hose after the hose has been cut?
It is greater than FN because the water exiting the hole exerts a downward force on the hose.
A person is in a cubical room that is 3m on a side. A horizontal electric field exists in the room. The person measures the potential difference between the middle of the door on one side of the room and a point at the same height on the opposite wall as 9V, with the door at a higher potential. What are the magnitude and direction of the average electric field in the room?
Magnitude - 3V/m Direction - From the door to the wall
Students are performing an experiment with charged objects. They have two charged objects, A and B, each in an insulating box. In addition, they have a small, light, charged sphere that hangs from insulating string. The students bring the sphere close to different sides of the box containing object A. They find that the sphere is always attracted to the object. The students then bring the sphere close to the box containing object B. They find that the sphere is attracted when held near one side of the box and repelled when held near the opposite side. Which of the following best describes the charge on the two objects?
Object A is a monopole, and object B is a dipole.
A volume ΔVΔV of an ideal fluid enters the left side of a cylindrical pipe with speed v1v1 during a time interval ΔtΔt, and an equal volume ΔVΔV of ideal fluid exits the right side of the pipe with speed v2v2 during the same time interval ΔtΔt. The cross-sectional areas of the left end and right end of the pipe are A1A1 and A2A2 , respectively; the pressures at the left end and right end of the pipe are P1P1 and P2P2 , respectively; and the distance between the centers of the two sections is ΔhΔh , as shown in the figure. Which equation and description best expresses the motion of the ideal fluid in the cylindrical pipe in terms of conservation of energy?
P1+1/2ρv1^2=P2+ρgΔh+1/2ρv2^2 . The speed of a fluid at two different locations in a pipe depends on the pressure of the fluid at each location and the work done by gravity on the fluid as it moves from one location to the other.
Students rub air-filled balloons on their hair and then touch the charged balloons to the ceiling. The balloons initially stick to the ceiling but after some time eventually fall back down. Which of the following claims best describes the physical processes responsible for these observations?
The balloons induced charge separation in the ceiling, resulting in an attractive force. Over time, conduction of electrons into the air reduced the net charge of the balloons.
Two negatively charged balloons are suspended from the ceiling by insulating strings, as shown in figure 1. Free-body diagrams showing the tension force FT , electric force FE , and gravitational force Fg on each balloon are shown in figure 2. If the amount of negative charge on each balloon increases, how should the length of the vectors shown in the figure be changed?
The electric and tension force vectors should be longer, and the gravitational force vector should remain the same.
Two point charges with charges Q1=+2μC and Q2=−4μC are located on the horizontal axis, as shown in the figure. The distance between their centers is 1.0m. Point P is midway between the point charges. How will the component of the electric field at point P due to Q1Q1 change, if at all, if the distance between point P and Q1Q1 is halved?
The electric field will quadruple because the electric field strength is inversely proportional to the square of the distance.
The figures show situation 1 and 2. In situation 1, a positively charged 0.10kg insulating sphere is suspended at rest 0.10m above a large positively charged metal plate. In situation 2, a positively charged 0.20kg insulating sphere is located 0.20m above the positively charged metal plate and is in motion. The magnitudes of the charges on the spheres are the same. Which of the following best explains why sphere 1 can remain motionless?
The electric force between sphere 1 and the positively charged plate is equal to the force of gravity between sphere 1 and Earth.
Ice cubes are added to an insulated cup of hot water. As a result, the temperature of the water decreases and the ice melts. What statement best explains the change in entropy of the system, which is the combination of water and ice cubes, on a molecular level?
The entropy of the system increases, because the disorder caused by the change in state from solid to liquid water causes more disorder than liquid water cooling causes order.
Water enters the intake hose of a rotating sprinkler with two outlets, as shown in the figure. The density of the water is ρwρw , the height of the sprinkler arms above the intake hose is hh , the cross-sectional area of the hose is AinAin , and the total cross-sectional area of the outlets is AoutAout . The pressure inside the hose is PhPh and the pressure of the air near the outlets is PaPa . Assume that the effects of the viscosity of the water and friction are negligible. The valve connected to the hose is initially shut, so the sprinkler is off. Which of the following correctly explains whether an expression for the speed of the water exiting the outlets can be determined with the variables provided?
The exit speed can be determined because the difference in pressure, the difference in height, and the ratio of the cross-sectional areas of the inlet and outlet hoses are known.
Two identical spheres, sphere AA and sphere BB, are suspended from insulating threads. The charge on sphere AA has the same sign and twice the magnitude as the charge on sphere BB. The spheres are at rest. A student draws a free-body diagram to represent the forces acting on the spheres. Which of the following describes a change that should be made to the diagram to make it correct?
The force diagram the student has drawn indicates a net horizontal force on each sphere. FE,A should be drawn with length equal to the horizontal component of FT,A, and FE,B should be drawn with length equal to the horizontal component of FT,B
Small, negatively charged plastic beads are launched horizontally beneath a flat, positively charged plate, as shown in the figure. The beads follow various paths in the region beneath the plate. A student is asked to explain a calculation of the magnitude of the external force that must be exerted on the plate to keep it stationary. Which of the following lists the forces in the explanation that must be added to determine the external force?
The gravitational force that Earth exerts on the plate and the force the beads exert on the plate
The figure shows isolines of electric potential around four spheres with charges of the signs shown. The relative magnitudes of the masses of the spheres are the same as the relative magnitudes of their charges. Which of the following best describes the isolines of gravitational potential of the spheres?
The gravitational isolines are the same as the electric isolines for four negative charges of these magnitudes.
A beaker partially filled with water rests on a scale. A metal block is lowered into the water by a string until it is fully submerged. Which of the following correctly explain why the reading on the scale increases? Select two answers.
The higher water level causes a greater pressure on the bottom of the beaker. The block exerts a downward force on the water equal to the buoyant force on the block.
A pipe of radius RA carries water moving at a speed vA at point A. The pipe then narrows to a smaller radius RB and travels upward a distance H to point B, where the water is moving at speed vB. Which of the following gives correct reasoning about the water's properties as it moves from point A to point B?
The increase in gravitational potential energy of the water-Earth system and in the kinetic energy of the water causes a decrease in water pressure.
One mole of an ideal gas is sealed in a cylinder with a moveable piston. The temperature of the gas inside the cylinder increases from 0°C to 100°C as the gas expands, as shown in the figure. Which of the following correctly justifies the change, if any, of the internal energy of the gas?
The internal energy of the gas increases because the average kinetic energy of the gas molecules increases.
A sample of N molecules of ideal gas expands with no energy transferred into or out of the gas by heating. The pressure and volume of the gas are measured as it expands, and a graph of pressure as a function of volume is used to calculate the work done by the gas. Which of the following indicates a quantity for the gas that can be determined using the calculated work and justifies why it can be determined? Select two answers.
The magnitude of the change in internal energy of the gas can be determined. If no energy is transferred by heating, the magnitude of the change in internal energy equals the magnitude of the work done by the gas. The magnitude of the change in the average kinetic energy of a molecule of the gas can be determined. The magnitude of the total change in the kinetic energy of the gas molecules is equal to the magnitude of the work done by the gas, and the magnitude of the change in the average kinetic energy of one molecule is the magnitude of the total change in kinetic energy divided by the number of molecules.
Water enters the intake hose of a rotating sprinkler with two outlets, as shown in the figure. The density of the water is ρw , the height of the sprinkler arms above the intake hose is h , the cross-sectional area of the hose is Ain , and the total cross-sectional area of the outlets is Aout . The pressure inside the hose is Ph and the pressure of the air near the outlets is Pa . Assume that the effects of the viscosity of the water and friction are negligible. The valve connected to the hose is initially shut, so the sprinkler is off. The valve is opened and water flows out of the sprinkler outlets at a constant rate. Which of the following best explains why the sprinkler begins rotating?
The magnitude of the momentum change of the water per unit time is equal to the magnitude of the momentum change of the sprinkler per unit time.
Two charged particles, X and Y, are placed near each other and released from rest. Particle Y has twice the mass and twice the charge that particle X has. Which of the following best explains why the acceleration of particle Y is half that of particle X?
The particles exert forces on each other that have the same magnitude. The mass of particle Y is twice that of particle X, so the acceleration of particle Y is half that of particle X.
A hot rock is placed on an insulating stand inside of a small vacuum chamber. The air inside the chamber is quickly removed. Over time, the sides of the container become warmer and the rock becomes cooler. Which of the following models best describes the primary mode of energy transfer in this process?
The rock emits radiant energy that is absorbed by the walls of the container.
A student predicts that the density of salt water is higher than the density of drinking water. The student has a beaker filled with salt water, a beaker filled with drinking water, and a cube that is hung from a spring scale. The cube will sink in both liquids. What measurements are needed to verify the student's prediction?
The spring scale reading with the cube submerged in each liquid only
The figure shows a conducting sphere with net charge +Q and points A and B. At point A , the electric field has a magnitude of 40N/C . At point B the electric field has a magnitude of 10N/C. Which of the following is most directly related to why the field at B is 1/4 the field at A?
The surface area of a sphere centered at the center of the conducting sphere and passing through B is four times the surface area of a similar sphere passing through A.
Isolines of the electric potential due to two point charges, represented by dots, are shown. The point charges have equal magnitudes and unknown signs. If the electric potential is zero at an infinite distance from the charges, which of the following is true about the electric potential V and the magnitude E of the electric field midway between the charges?
V≠0 and E=0
The figure shows a proton p and an electron e that are at rest on a line in the plane of the page. They are between two large uncharged parallel plates (not shown). Assume the particles are far apart so that their mutual gravitational and electrostatic forces are negligible. A potential difference is now established between the plates, and as a result an electric field directed toward the top of the page is created. Which of the following describes the velocity of the center of mass of the particles before either of them hits one of the plates?
Zero
