AP Physics/Final Test/Sem. 2

The particles exert both electrical and gravitational forces on one another because they have both charge and mass. Any two object with charge and any two objects with mass will exert forces on each other.

A container holds electrically charged gas particles at high temperature. Which of the following correctly describes the interactions between the particles?

Velocity: v1 < v2 Pressure: p1 > p2

A fluid flows steadily from left to right in the pipe shown above. The diameter of the pipe is less at point 2 then at point 1, term-0 and the fluid density is constant throughout the pipe. How do the velocity of flow and the pressure at points 1 and 2 compare?

πr^2vt

A fluid flows through a pipe of radius r at a speed v for a time t. The volume of fluid that flows past a point in the pipe during this time is equal to

−3/2v0 The system's momentum before the collision is the same as the momentum after the collision: mv0−(5m)(2v0)= (m+5m)vfmv0−(5m)(2v0)=(m+5m)vf , so vf = −3/2v0v f= −3/2v0 .

A gas contains two types of particles. Particle A has mass m and velocity v0 in the +z-direction. It collides head-on with particle B that has mass 5m and velocity 2v0 in the −z-direction. Electrostatic force then holds the particles together. What is the final velocity of the two-particle system?

300 J

A gas undergoes an expansion in which 400 J of energy is added to the gas by heating. The internal energy of the gas changes from 700 J to 800 J. The work done by the gas is

It decreases by 48 J.

A gas with a fixed number of molecules does 32 J of work on its surroundings, and 16 J of heat are transferred from the gas to the surroundings. What happens to the internal energy of the gas?

A straight path toward the north and angled upward Correct. The gas-filled balloon is less dense than the air, so there is an upward force exerted on it. The breeze exerts a northward force. So there is a net force exerted on the balloon that is upward and to the north, which causes the balloon to move straight in that direction.

A gas-filled balloon has a total average density of 0.2ρ. The air surrounding the balloon has a density of ρ. The balloon is released from rest in a constant horizontal breeze directed north. If air resistance is negligible, what is the shape of the path followed by the balloon?

Thermometer and pressure gauge The ideal gas law (PV=nRTPV=nRT) involves pressure PP and temperature TT. Thus, a pressure gauge would measure pressure, and a thermometer would measure temperature. Ruler and sealed cylinder The ideal gas law (PV=nRTPV=nRT) involves volume VV and the number of moles n n of gas molecules. Volume can be calculated from the sealed cylinder's radius and height measurements, taken with the ruler. Using the molar density chart, nn could then be calculated.

A group of students plans to take measurements on a gas and record data that can be graphed in order to estimate the universal gas constant R from a graph. Along with a molar density chart, which two of the following combinations would the students need for their experiment? Select two answers.

9.0 X 10^3 N/C

A hollow metal sphere 1.0 m in diameter carries a charge of 4.0 µC.The electric field at a distance of 2.0 m from the center of the sphere is most nearly

FG /FE does not change; it is the same nonzero value for all separations

A hydrogen atom is isolated in a vacuum chamber. The electron is now separated from the proton and moved to a distance 1 cm away. Let FG be the magnitude of the gravitational force between the proton and electron, and let FE be the magnitude of the electric force between the proton and electron. How does the ratio FG /FE change as the particles are separated?

Student BB. 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.

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 A says that the force exerted by individual molecules as they bounce off the wall is always perpendicular to the wall. Student B says that the molecules may strike the wall at angles that are not perpendicular. Which student is correct and why?

7.7 × 103 N This option is correct. The minimum upward force is equal to the net downward force on the lid, which is the sum of the weight of the lid and the net downward force due to air. The pressure outside is greater than pressure inside, so net pressure times the area of the lid is net force due to air. ΣFup = ΣFdown = (1.01 × 105 - 0.40 × 105)( πr2) + 200N = 7.7 × 103N

A partially evacuated vertical cylindrical container is covered by a circular lid that makes an airtight seal. The pressure in the room surrounding the container is 1.01 × 105 N/m2, and the pressure inside the container is 0.41 × 105 N/m2. The lid has radius 0.20 m and weight 200 N. The minimum upward applied force required to lift the lid is most nearly

Momentum 16mv Kinetic Energy 23mv^2 Collisions of ideal gas atoms are elastic, conserving momentum and kinetic energy. So the values of total momentum and kinetic energy are the same before and after the collision. The momentum is mv+(5m)(3v)=16mvmv+(5m)(3v)=16mv. The kinetic energy is 12mv2+12(5m)(3v)2=23mv212mv2+12(5m)(3v)2=23mv2.

A scientist has two well-insulated containers, one filled with atoms of ideal gas X and the other with atoms of ideal gas Y. The gas X atoms have mass m, and the gas Y atoms have mass 5m. The containers are then connected so that the gases mix together. A gas X atom with speed v collides with a gas Y atom with speed 3v. Which of the following correctly indicates the total momentum and kinetic energy of the two atoms after the collision?

Some molecules will speed up and others will slow down, keeping the average kinetic energy of the molecules constant. This option is correct. If the room temperature is constant and the container and air are in equilibrium, the average translational kinetic energy of molecules remains constant. However, speeds of individual molecules will vary due to collisions between them.

A sealed container of air has been sitting on a table in a dark room for a very long time. The room is always kept at a constant temperature. Which of the following best describes what will happen to the speeds and the average kinetic energy of the molecules of the air in the container as the container continues to sit on the table?

P as a function of 1/V

A series of measurements are made of the pressure P and the volume V of a sample of nitrogen gas kept at a constant temperature. It is desired to represent the data graphically so that the graph will be a straight line if the behavior of the gas is ideal. Accordingly, which of the following should be plotted?

The metal slab feels colder to the student because it conducts thermal energy away from the student's hand faster, but the slabs have the same temperature. This option is correct. The slabs are in thermal equilibrium with the room and at the same temperature, but perception of temperature depends on the rate of thermal energy transfer. Metal has higher thermal conductivity than wood, so it feels colder when touched by the warmer hand of the student.

A slab of metal and a slab of wood are placed in a classroom and allowed to sit undisturbed for a long time. A student then places one hand on the metal and the other hand on the wood. Which of the following describes the student's perception of the temperatures of the slabs and their actual temperatures?

Conducting: Spread over the surface Insulating: At the top

A small amount of charge is placed on both an isolated conducting sphere and an isolated insulating sphere. For both spheres, the charge is added at a small area at the top of the sphere. After a few seconds, where on each of the spheres is the charge that was added?

The sphere must be negatively charged. Like sign charges attract and opposite sign charges repel, so the sphere must have a negative charge.

A student has a small metal sphere that hangs from an insulating string. In seeking to determine the charge on the sphere, the student brings a positively charged rod near the sphere and finds that the sphere is attracted to the rod. The student then brings a negatively charged rod near the sphere and finds that the sphere is repelled by the rod. Which of the following conclusions, if any, can be drawn from the results?

The spring scale reading with the cube submerged in each liquid only The denser liquid will exert a greater buoyant force. Therefore, the spring scale reading will be less in the denser liquid. If one wants to find out only which liquid is denser, that is the only comparison that needs to be made.

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 gas is compressed at a constant pressure of 200 kPa.

A student writes the following information for a process that involves a fixed quantity of ideal gas. W = −PΔV ΔU = Q + W P = 2.0x10^5 Pa ΔV = - 2.0x10^-3 m^3 ΔU = - 600 J Which of the following descriptions best represents the process?

I only it will expand.

An air-filled balloon is placed at rest on the bottom of an open vacuum chamber. The chamber is then sealed and most of the air is removed. Which of the following will happen to the balloon? I. It will expand. II. Its temperature will increase. III. It will rise from the bottom.

Was there some systematic experimental uncertainty in the procedure or analysis? Since each object seems to have the same +0.3e+0.3e unit of charge, there might be some problem that is affecting all the measurements in the same way. Is there some unknown particle present that has a charge that is a non-integer multiple of e ? Correct. Although an isolated charge smaller than the elementary charge has not been found, results that seem to suggest its existence should be examined closely to be sure this not the cause.

An experiment is conducted to find the net charge on a number of identical, isolated, microscopic objects that have been charged by induction. The researchers perform an analysis and determine that the best estimate of the net charge on each object is +(n+0.3)e , where n is an integer and e is the elementary charge. Which of the following are questions the scientists should explore to try to refine their results? Select two answers.

Average Kinetic Energy: Increases Volume: Increases

An ideal gas in a closed container of variable volume experiences an increase in temperature while the pressure remains unchanged. What happens to the average kinetic energy of the molecules and the volume of the gas as the temperature increases?

I only the change in internal energy of the gas

An ideal gas may be taken from one state to another state with a different pressure, volume, and temperature along several different paths. Quantities that will always be the same for this process, regardless of which path is taken, include which of the following? I. The change in internal energy of the gas II. The heat exchanged between the gas and its surroundings III. The work done by the gas

2Nmv / A∆t

An ideal gas with molecules of mass m is contained in a cube with sides of area A. The average vertical component of the velocity of the gas molecules is v, and N molecules hit the side of the cube in a time ∆t . What is the pressure exerted by the gas on the bottom of the cube?

PA∆t/2Nm

An ideal gas with molecules of mass m is contained in a cube with sides of area A. The pressure exerted by the gas on the top of the cube is P, and N molecules hit the top of the cube in a time ∆t. What is the average vertical component of the velocity of the gas molecules?

It does not change because the internal energy of an ideal gas depends only on its temperature.

An ideal monatomic gas is compressed while its temperature is held constant. What happens to the internal energy of the gas during this process, and why?

On average, the molecules of gas 1 lose some of their kinetic energy to the molecules of gas 2 through collisions, resulting in the two gases eventually having the same temperature.

An insulated container with a divider in the middle contains two separated gases. Gas 1 is initially at a higher temperature than gas 2. The divider is then removed. Which of the following observations might be made over a period of time as the two gases mix together, and why?

Air moves from the lower opening toward the higher opening.

An underground tunnel has two openings, with one opening a few meters higher than the other. If air moves past the higher opening at a greater speed than it moves past the lower opening, what happens inside the tunnel?

The mass flow rate is constant. (The continuity equation relies on the assumption that the mass flow rate is the same everywhere, which is a statement of mass conservation.) The fluid is incompressible. (The continuity equation relies on the assumption that the fluid is incompressible and therefore has the same density everywhere)

The continuity equation indicates that the speed of a fluid flowing through a pipe will change when the cross-sectional area of the pipe changes. Which of the following assumptions justify the use of the continuity equation? Select two answers.

II only

The diagram above shows a pipe with an ideal fluid in motion to the right. As the fluid enters region II, which of the following quantities related to the fluid will increase? I. Pressure II. Linear speed III. Volume rate of flow

800 K

A sample of gas has a temperature of 200 K. If the speed of every gas molecule in the sample is doubled, what is the new temperature of the gas?

A force of repulsion between electrons in the neutral atoms of the block and electrons in the neutral atoms of the water

A block floating in water is supported by the buoyant force exerted on the block by the water. The buoyant force is created on the atomic scale primarily by which of the following electrostatic forces?A force of repulsion between electrons in the neutral atoms of the block and electrons in the neutral atoms of the water

FE>FgFE>Fg, because the product of the charge of an electron and the Coulomb's law constant kk is greater in magnitude than the product of the mass of an electron and the universal gravitational constant GG.

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?

Negative

A positively charged rod is initially far from a neutral, grounded conductor and is then brought close to the conductor without touching it. If the ground wire is removed while the charged rod is near the conductor, what is the net charge on the conductor?

6 x 10^5 Pa

A sealed container with a lid of area 0.004 m^2 is filled with an ideal gas. The container and gas are allowed to reach thermal equilibrium with the surrounding air. If a 2000 N block is needed to keep the lid from being pushed off the container, what is the absolute pressure inside the container (the pressure compared to vacuum) ?

Bring the rod near the right side of B. Touch A to the left side of B. Remove B and then remove the rod. This option is correct. The positive rod attracts electrons to the right side of B leaving the left side positively charged. Touching A to B allows electrons from A to move to the left side of B. When B is removed from A, A is left with a net positive charge, which is the desired outcome.

A student has a positively charged insulating rod and two initially uncharged conducting spheres, A and B, with insulated handles. Which of the following ordered sequences of actions could the student use to produce a net positive charge on sphere A ?

When it is completely underwater

A large rock thrown into a pool of water of uniform density becomes completely submerged and then sinks to the bottom. When is the buoyant force on the rock the greatest?

always less than W

A solid object of mass m is suspended vertically from a spring balance. The spring balance reads W when the object is in air. When the object is submerged in water while still attached to the balance, the reading on the balance is

Push the piston in rapidly. The temperature of the gas will increase because no energy will be transferred to the surroundings by cooling.

A student wants to increase the temperature of an ideal gas in a cylinder that is initially at room temperature. The cylinder has a movable piston with negligible friction. Which of the following correctly indicates an action the student could take to increase the temperature of the gas, and why the temperature increases?

F as a function of 1/d^2

A very small, isolated sphere with charge +Q exists in an empty region of space. A second very small sphere is moved from far away to a short distance from the first sphere As the second sphere is moved at a constant velocity closer to the first sphere, data is taken for the force F exerted on the second sphere by the first sphere as a function of the separation d of the spheres. Which of the following should be graphed to yield a straight line from the data?