Physics Review for Test 04

Masses are distributed in the xy-plane as follows: 10 kg at (2.0, 6.0) m, 4.0 kg at (2.0, 0.0) m, and 6.0 kg at (0.0, 3.0) m. Where would a 20-kg mass need to be positioned so that the center of gravity of the resulting four mass system would be at the origin?

(-1.4, -3.9) m

A hoop of radius 1.0 m is placed in the first quadrant of an xy-coordinate system with its rim touching both the x-axis and the y-axis. What are the coordinates of its center of gravity?

(1.0, 1.0) m

A certain metal has a specific heat c = 0.21 cal/goC and a mass m = 25.6 g. The initial temperature is Ti = 34.6oC, and the final temperature Tf = 54.6oC. The quantity of heat absorbed is

+110 cal

A uniform stick 1 m long is placed horizontally on the ground along an east-west axis. A force of 1.0 N is applied to the center of the stick in a direction 30º west of north. The torque exerted by the force relative to the east end of the stick is

-0.43 Nm

A 3.0-m rod is pivoted about its left end. A force of 6.0 N is applied perpendicular to the rod at a distance of 1.2 m from the pivot causing a ccw torque, and a force of 5.2 N is applied at the end of the rod 3.0 m from the pivot. The 5.2 N is at an angle of 30° to the rod and causes a cw torque. What is the net torque about the pivot?

-0.6 Nm

The temperature in January in Winnipeg, Manitoba, has been known to go down to -40ºC. What is this temperature on the Fahrenheit scale?

-40°F

Two children seat themselves on a seesaw. The one on the left has a weight of 400 N while the one on the right weighs 300 N. The fulcrum is at the midpoint of the seesaw. If the child on the left is not at the end but is 1.50 m from the fulcrum and the seesaw is balanced, what is the torque provided by the weight of the child on the right?

-600 Nm

The angular momentum of a body about a particular axis as a function of time is shown in the graph. The external torque acting on the body along this axis at t = 5 s is

0 Nm

A 250-g piece of lead is heated to 100oC and is then placed in a 400-g copper container holding 500 g of water. The specific heat of copper is c = 0.386 kJ/kgK. The container and the water had an initial temperature of 18.0oC. When thermal equilibrium is reached, the final temperature of the system is 19.15oC. If no heat has been lost from the system, what is the specific heat of the lead? (the specific heat of water is 4.180 kJ/kgK)

0.128 kJ/kgK

Consider Earth as a uniform sphere of radius 6371 km, with a mass of th e5.98z10^24 kg, and a rotational period of 1 day. If Earth suddenly had a diameter of half this value without any loss of mass, calculate the new period of rotation.

0.25 days

A ping-pong ball has an average density of 0.0840 g/cm3 and a diameter of 3.80 cm. What force would be required to keep the ball completely submerged under water?

0.258 N

A hypodermic needle can be thought of as a large area pipe leading to a small area pipe that opens into the vein. The diameter of the plunger is 1.2 cm and the needle diameter is 0.15 cm. If the gauge pressure in the vein is 25 mmHg, what minimum force is needed on the plunger in order for a fluid flow into the vein to occur?

0.38 N

To raise the temperature of a 2.0-kg piece of metal from 20o to 100oC, 61.8 kJ of heat is added. What is the specific heat of this metal?

0.39 kJ/kgK

An athlete can twirl a baton so that it reaches an angular velocity of 12 rad/s from rest in 0.5 s. If the length of a uniform baton is 0.8 m and the mass is 0.5 kg, what is the torque needed to reach the angular velocity?

0.64 Nm

Tasha has mass 20 kg and wants to use a 4.0-m board of mass 10 kg as a seesaw. Her friends are busy, so Tasha seesaws by herself by putting the support at the system's center of gravity when she sits on one end of the board. How far is she from the support point?

0.67 m

A meter stick is pivoted at the 0.50-m line. A 3.0-kg object is hung from the 0.10-m line. Where should a 5.0-kg object be hung to achieve equilibrium?

0.74-m line

A thin, massless string is wrapped around a 0.25m radius grindstone supported by bearings that produce negligible frictional torque. A steady tension of 20 N in the string causes the grindstone to move from rest to a speed of 60 rad/s in 12s. The moment of inertia of the grindstone is

1 kgm^2

A Boeing-737 airliner has a mass of 20 000 kg. The total area of the wings is 100 m^2. What must be the pressure difference between the top and bottom of the wings to keep the airplane up?

1,960 Pa

Masses are distributed in the x,y-plane as follows: 6.0 kg at (0.0, 0.0) m, 4.0 kg at (2.0, 0.0) m, and 5.0 kg at (2.0, 3.0) m. What is the x-coordinate of the center of gravity of this system of masses?

1.2 m

At the core of the Sun, the pressure is 2.53x1016 Pa and the temperature is 1.56x107 K. Assume that the ideal gas law is valid for this situation. What is the particle density (particles/m3) at the core of the Sun?

1.2 x 10^32

As part of a science project you investigate the effect of punching holes in a plastic container of water and observing the flow of liquid out of the different holes. If the container has a water level 20 cm above the base and you punch a hole in the side 12 cm high, calculate the speed at which water will initially flow out of the hole.

1.25 m/s

When the temperature of an ideal gas is increased from 300 K to 400 K, the average kinetic energy of the gas molecules increases by a factor of

1.33

A woman who weighs 500 N stands on an 8.0-m-long board that weighs 100 N. The board is supported at each end. The support force at the right end is 3 times the support force at the left end. How far from the right end is the woman standing?

1.6 m

The internal energy of a monatomic gas is 1.0 J. The temperature of the gas is 298 K. How many particles are there in the gas?

1.6x10^20

A lake with 8.0x109 kg of water, which has a specific heat of 4180 J/kgoC, warms from 10o to 15oC. The amount of heat transferred to the lake is

1.7x10^14 J

A hole is poked through the metal side of a drum holding water. The hole is 18 cm below the water surface. What is the initial speed of outflow?

1.9 m/s

Two ideal gases, X and Y, are thoroughly mixed and at thermal equilibrium in a single container. The molecular mass of X is 9 times that of Y. What is the ratio of root-mean-square velocities of the two gases, vX, rms/vY, rms?

1/3

A wheel is rotating freely with an angular speed of 20 rad/s on a shaft whose moment of inertia is negligible. A second identical wheel, initially at rest, is suddenly coupled to the same shaft. The angular speed of the coupled wheels is

10 rad/s

How deep under the surface of a lake would the pressure be double that at the surface? (1 atm = 1.01x105 Pa)

10.3 m

What is the weight of water displaced by a 100-ton floating ship?

100 tons

A 3-kg mass of metal of specific heat = 0.1 kcal/kgoC at a temperature of 600oC is dropped into 1.0 kg water at 20oC. With no heat losses to the surroundings, determine the equilibrium temperature of the mixture, and if it is 100oC, calculate what mass of water is turned into steam at this temperature.

100°C and 130 g of steam

The graph shows the temperature of a 75.0-g sample of material as thermal energy is added to it. The material is initially a solid. The pressure remains constant, and there is no chemical change. The latent heat of vaporization is

107 kJ/kg

A 3.00-g lead bullet is traveling at a speed of 240 m/s when it embeds in a wood post. If we assume that half of the resultant heat energy generated remains with the bullet, what is the increase in temperature of the embedded bullet? (specific heat of lead = 128J/kgK)

113°C

A rotating flywheel can be used as a method to store energy. If it is required that such a device be able to store up to a maximum of 1.00x10^6 J when rotating at 400 rad/s, what moment of inertia is required?

12.5 kgm^2

A 2.0-kg mass of iron (specific heat = 0.12 kcal/kgoC) at a temperature of 430oC is dropped into 48 kg of water. The water is initially at a temperature of 10oC. With no heat losses to the surroundings, the equilibrium temperature of the iron and water is approximately

12°C

The pressure inside a commercial airliner is maintained at 1.00 atm (105 Pa). What is the net outward force exerted on a 1.0 m x 2.0 m cabin door if the outside pressure is 0.30 atm?

140,000 N

A small sphere of wood with a density r = 0.40 g/cm3 is held at rest well under the surface of a pool of water. The magnitude of the initial acceleration of the sphere when it is released is

15 m/s2

The graph shows the temperature of a 75.0-g sample of material as thermal energy is added to it. The material is initially a solid. The pressure remains constant, and there is no chemical change. The specific heat of the liquid phase is

152 J/kg°C

A 4.0-kg mass is placed at (3.0, 4.0) m, and a 6.0-kg mass is placed at (3.0, -4.0) m. What is the moment of inertia of this system of masses about the x-axis?

160 kgxm^2

The mean of the squares of the velocity in the x-direction for a gas has the value of 1800 m2/s2. What is the value for the mean of the squares of the velocity in the z-direction? .

1800 m2/s2

A 6.0-g lead bullet traveling at 300 m/s penetrates a wooden block and stops. If 50 percent of the initial kinetic energy of the bullet is converted into thermal energy in the bullet, by how much does the bullet's temperature increase? (The specific heat of lead is 128 J/kgK.)

180°C

Calculate the point on the Fahrenheit scale when numerically it is 100 degrees larger than that of the Celsius scale for the same temperature.

185°F

The temperature gradient in a wall is 80 Cº/cm, and the thermal conductivity of this wall is 4.0x10-3 cal/scmCº. The amount of heat conducted per minute per square centimeter through this wall is approximately

19 cal

A spinning skater draws in her outstretched arms thereby reducing her moment of inertia by a factor of 2. Determine the ratio of her final kinetic energy to her initial kinetic energy.

2

Carly places one end of a steel bar in a Bunsen flame and the other end in an ice cube. By what factor is the rate of heat flow changed when the bar's cross-sectional area is doubled?

2

The graph shows the Maxwell-Boltzmann distribution function of the number of gas molecules per unit speed range for two different temperatures. Which gas has a higher temperature?

2

The vessels in the figure contain liquids of the same density. The vessel that has the greatest pressure at its base is

2

A rock suspended by a string weighs 5 N out of water and 3 N when submerged. What is the buoyant force on the rock?

2 N

The graph shows the Maxwell-Boltzmann distribution function of the number of gas molecules per unit speed range at a given temperature. The average speed, the most probable speed, and the rms speed (in this order) are most likely given by

2, 1, 3

A room measures (3.0 m) x (4.0 m) x (2.0 m) and is at 15°C and normal air pressure (101,325 Pa). When the temperature is increased to 25°C, the number of molecules that escaped from the room is, assuming that the pressure stays at normal air pressure

2.1x10^25

A cube of wood of density 0.78 g/cm^3 is 10 cm on a side. When placed in water, what height of the block will float above the surface? (water density = 1.00 g/cm^3)

2.2 cm

A 1500-kg satellite orbits a planet in a circular orbit of radius 6.2x106 m. What is the angular momentum of the satellite in its orbit around the planet if the satellite completes one orbit every 1.5x104 s?

2.4x10^13 kgm^2/s

An 800-N billboard worker stands on a 4.0-m scaffold weighing 500 N and supported by vertical ropes at each end. How far would the worker stand from one of the supporting ropes to produce a tension of 550 N in that rope?

2.5 m

The sign in the figure weighs 240 N. The boom is of uniform construction. The boom has a mass of 39 kg and is 2.8 m in length. The angle between the tie cable and the beam is 27o. What is the tension in the tie cable?

2.7 kN

A hoop rotates about an axis through its center with an angular velocity of 40.0 rad/s. If the rotational kinetic energy of the hoop is 400 J, its angular momentum is

20 kgm^2/s

Two liquids, A and B, are mixed together. Liquid A has mass m and was initially at temperature 40oC, and liquid B has mass 2m and was initially at temperature 5oC. The specific heat of liquid A is 1.5 times that of liquid B. Calculate the final temperature of the mixture.

20..0 °C

960 J = _____ cal.

229

A vault is opened by applying a force of 300 N perpendicular to the plane of the door, 0.80 m from the hinges. Find the torque due to this force about an axis through the hinges.

240 Nm

The mean of the squares of the velocity in the y-direction for a gas has the value of 2400 m2/s2. What is the value for the mean of the squares of the velocity in the x-direction?

2400 m2/s2

The mean of the squares of the velocity in the x-direction for a gas has the value of 800 m2/s2. What is the value for the mean of the squares of the total velocity?

2400 m^2/s^2

Water is drawn from a well in a bucket tied to the end of a rope whose other end wraps around a cylinder of mass 50 kg and diameter 25 cm. As you turn this cylinder with a crank, the rope raises the bucket. If the mass of a bucket of water is 20 kg, what torque must you apply to the crank to raise the bucket of water at a constant speed?

25 Nm

A long steel beam has a length of twenty-five meters on a cold day when the temperature is 0°C. What is the length of the beam on a hot day when T = 40°C? (asteel = 1.1x10-5/C°)

25.011 m

A 4.0-kg mass is placed at (3.0, 4.0) m, and a 6.0-kg mass is placed at (3.0, -4.0) m. What is the moment of inertia of this system of masses about the z-axis?

250 kgm^2

A uniform bridge span weighs 50.0 kN and is 40.0 m long. An automobile weighing 15.0 kN is parked with its center of gravity located 12.0 m from the right pier. What upward support force does the left pier provide?

29.5 kN

A single atom of Krypton has a mass of 1.39x10-25 kg. The temperature of Krypton gas is 298 K. What is the root mean square velocity of the gas?

298 m/s

What is the temperature increase of 4.0 kg of water when heated by an 800-W immersion heater for 10 min? (cw = 4 186 J/kg°C)

29°C

A disc is free to rotate about an axis. A force applied at a distance d from the axis causes an angular acceleration αα. What angular acceleration is produced if the same force is applied a distance 2d from the axis?

2a

The graph shows the Maxwell-Boltzmann distribution function of the number of gas molecules per unit speed range at a given temperature. The rms speed is most likely given by

3

The vessels in the figure contain liquids of the same density. The vessel that has the least pressure at its base is

3

Which of the objects is nearest to being in unstable equilibrium?

3

The configuration(s) that is/are in unstable equilibrium is/are

3 and 5

Dmitri places one end of a copper rod in a heat reservoir and the other end in a heat sink. By what factor is the rate of heat flow changed when the temperature difference between the reservoir and sink is tripled?

3.0

A merry-go-round with a moment of inertia of 6.78x103 kgm2 is coasting at 2.20 rad/s. When a 72.6-kg man steps onto the rim, the angular velocity decreases to 2.0 rad/s. The radius of the merry-go-round is

3.06 m

In a vacuum system, a container is pumped down to a pressure of 1.33x10-6 Pa at 20ºC. How many molecules of gas are there in 1 cm3 of this container?

3.3x10^8

A uniform 1.0-N meter stick is suspended horizontally by vertical strings attached at each end. A 2.0-N weight is suspended from the 10-cm position on the stick, another 2.0-N weight is suspended from the 50 cm position, and a 3.0-N weight is suspended from the 60 cm position. What is the tension in the string attached at the 100-cm end of the stick?

3.5 N

The surface of the Sun has a temperature of about 5,800 K. If the radius of the Sun is 7x108 m, determine the power output of the sun. (Take e = 1, and σ = 5.67x10-8 W/m2×K4).

3.95x10^26 W

A meter stick is supported by a knife-edge at the 50-cm mark. Doug hangs masses of 0.40 and 0.60 kg from the 20-cm and 80-cm marks, respectively. Where should Doug hang a third mass of 0.30 kg to keep the stick balanced?

30 cm

The highest and lowest temperatures ever recorded in the United States are 134ºF (California, 1913) and -80ºF (Alaska, 1971). What are these temperatures in kelvins?

330 K and 211 K

Two pistons of a hydraulic lift have radii of 2.67 cm and 20.0 cm. The downward force on the 2.67-cm piston that is required to lift a mass of 2000 kg supported by the 20-cm piston is

350 N

A temperature change from 15°C to 35°C corresponds to what incremental change in °F?

36

The mean of the squares of the velocity in the y-direction for a gas has the value of 1200 m2/s2. What is the value for the mean of the squares of the total velocity?

3600 m2/s2

The angular momentum of a flywheel about its axis is 925 kgm2/s. If its moment of inertia about the same axis is 2.50 kgm2, its angular velocity is

370 rad/s

Normal human body temperature is 98.6ºF. What is the corresponding Celsius temperature?

37°C

A solid wooden sphere of volume 0.0100 m3 floats freely exactly one-half submerged in a liquid of density 800 kg/m3. A lightweight cord is now tied to the sphere and is used to pull the sphere under the surface and hold it completely submerged. What is the tension in the cord?

39.2 N

A glass is filled with water. The gauge pressure at the top of the glass is zero and the gauge pressure at the bottom is P. A second glass with three times the height and twice the diameter is also filled with water. What is the pressure at the bottom of the second glass?

3P

A block of material has a density r. A second block of equal volume has three times the mass of the first. What is the density of the second block?

3p

A pipe of 2.54 cm inside diameter has a constriction in which the inside diameter is 1.27 cm. If water is flowing through this pipe with a velocity of 1.22 m/s in the main section, the velocity in the constricted section is

4.88 m/s

Five molecules of a gas have the following speeds: 200 m/s, 300 m/s, 400 m/s, 500 m/s, and 600 m/s. The rms speed for these molecules is

424 m/s

Five molecules of a gas have the following speeds: 200 m/s, 350 m/s, 400 m/s, 550 m/s, and 600 m/s. The rms speed for these molecules is

444 m/s

What constant torque, in the absence of friction, must be applied to a wheel to give it an angular velocity of 50. rad/s if it starts from rest and is accelerated for 10. s? The moment of inertia of the wheel about its axle is 9.0 kgm2.

45 Nm

Five molecules of a gas have the following speeds: 250 m/s, 350 m/s, 450 m/s, 550 m/s, and 650 m/s. The rms speed for these molecules is

472 m/s

A single molecule of Oxygen has a mass of 5.32x10-26 kg. The temperature of Oxygen gas is 298 K. What is the root mean square velocity of the gas?

482 m/s

Inside a sphere of radius 12 cm are 8.0x1023 gas molecules at a temperature of 50.0°C. What pressure do the gas molecules exert on the inside of the sphere?

490 kPa

A solid sphere of radius R rotates about a diameter with an angular speed w. The sphere then collapses under the action of internal forces to a final radius R/2. What is the final angular speed of the sphere?

4ω

A temperature difference of 5ºC is the same as a difference of

5 K

The angular momentum of a body about a particular axis as a function of time is shown in the graph. The external torque acting on the body along this axis at t = 2 s is

5 Nm

A ball bearing that has a density of 5.16 g/cm3 is held at rest under the surface of a liquid that has a density of 2.50 g/cm3. The magnitude of the acceleration of the ball bearing just after it is released is

5.0 m/s2

A steel wire, 150 m long at 10°C, has a coefficient of linear expansion of 11x10-6 1/oC. Calculate its change in length as the temperature changes from 10°C to 45°C.

5.8 cm

A tube with a radius of 4.2 cm is holding oil that has a density of 0.92 g/cm3. The pressure in the oil at a depth of 64 cm from the top of the surface is

5.8x103 Pa

A certain blackbody radiates 100 W at a temperature of 2000 K. How much power would this body radiate at 3000 K?

506 W

The graph shows the temperature of a 75.0-g sample of material as thermal energy is added to it. The material is initially a solid. The pressure remains constant, and there is no chemical change. The latent heat of fusion is

53 kJ/kg

The graph shows the temperature of a 75.0-g sample of material as thermal energy is added to it. The material is initially a solid. The pressure remains constant, and there is no chemical change. The specific heat of the solid phase is

533 J/kg°C

A person is losing thermal energy through the skin at a rate of 120 W when his skin temperature is 30°C. He puts on a sweater, and his skin temperature rises to 33°C. The effective thermal conductivity between his core and the environment changes from 0.22 W/mK to 0.18 W/mK. At what rate is he now losing thermal energy?

56 W

A piece of aluminum has density 2.70 g/cm3 and mass 775 g. The aluminum is submerged in a container of oil of density 0.650 g/cm3. A spring balance is attached with string to the piece of aluminum. What reading will the balance register in grams (g) for the submerged metal?

588 g

A 50-Nm torque acts on a wheel with a moment of inertia 150 kgm2. If the wheel starts from rest, how long will it take the wheel to make one revolution?

6.1 s

Your blood pressure is reported as 50 mm of Hg. The density of mercury is 13.6 g/cm^3. Your pressure is equivalent to

6.7x10^3 Pa

A 15,000-N car on a hydraulic lift rests on a cylinder with a piston of radius 0.20 m. If a connecting cylinder with a piston of 0.040-m radius is driven by compressed air, what force must be applied to this smaller piston in order to lift the car?

600 N

If the rms speed of oxygen molecules is 460 m/s at 0ºC, the rms speed of oxygen molecules at 273ºC is approximately

650 m/s

Body A has twice the mass and three times the specific heat of body B. They are supplied with equal amounts of heat. Body A experiences a temperature change ΔT. What change in temperature is experienced by body B?

6ΔT

A raft of density 700 kg/m3 has a surface area of 7.0 m2 and a volume of 0.7 m3. What depth does it sink into water of density 1000 kg/m3?

7 cm

Atmospheric pressure is 1.0x105 N/m2, and the density of air is 1.29 kg/m3. If the density of air is constant as you get higher and higher, calculate the height of the atmosphere needed to produce this pressure.

7,900 m

A disk with a radius of 1.5 m whose moment of inertia is 34 kgm^2 is caused to rotate by a force of 160 N perpendicular to the radius. The angular acceleration of the disk is approximately

7.1 rad/s^2

A horizontal pipe of 30 cm2 cross-sectional area carries water at a speed of 2.5 m/s. This pipe feeds a smaller pipe of cross section 10 cm2. Find the speed of water flow in the smaller pipe.

7.5 m/s

A uniform, horizontal beam of length 6.0 m and weight 120 N is attached at one end to a wall by a pin connection (so that it may rotate). A cable attached to the wall above the pin supports the opposite end. The cable makes an angle of 60° with the horizontal. What is the tension in the cable needed to maintain the beam in equilibrium?

70 N

The tension in the tie cable is 1.6 kN. The boom is of uniform construction. The boom has a mass of 29 kg and is 1.4 m in length. The angle between the tie cable and the beam is 33o. What is the mass of the sign?

74 kg

The tungsten filament of a light bulb has an operating temperature of about 2,100 K. If the emitting area of the filament is 1.0 cm2, and its emissivity is 0.68, what is the power output of the light bulb? (σ = 5.67x10-8 W/m2×K4)

75 W

If a student eats a fast food meal that has 762 food calories, how many heat calories does that equal?

762,000

A disc with moment of inertia I1 = 40 kgm2 and angular velocity w1 = 20 rad/s is dropped on to a stationary second disc along the axis of rotation. The second disc has moment of inertia I2 = 60 kg×m2. What is the angular velocity of the two discs after they collide and stick together?

8 rad/s

A constant torque of 16 Nm acts on an object with a moment of inertia of 2.0 kgm2. What is the angular acceleration of the object?

8.0 rad/s^2

A small lake has a surface area of 10000 m2. Assuming that the average depth of the lake is 2 m, how much heat is released when the average temperature of the water in the lake drops by 1oC?

8.36x10^10 J

A group of explorers in the Antarctic can obtain the water they need only by melting snow. How much heat does it take for them to make a cup of coffee (100 g water at 100oC)? Assume that the snow has an initial temperature of -40oC; that the latent heats of fusion and vaporization of water are, respectively, 333.5 kJ/kg and 2257 kJ/kg; and that the specific heats of ice (snow) and water are, respectively, 2.05 kJ/kgK and 4.18 kJ/kgK.

83 kJ

2,000 cal = _____ J.

8372

An 800-N billboard worker stands on a 4.0-m scaffold supported by vertical ropes at each end. If the scaffold weighs 500. N and the worker stands 1.0 m from one end, what is the tension in the rope nearest the worker?

850 N

Modern railway tracks consist of continuous welded-steel rails of 1.0-km lengths. If the coefficient of linear expansion of steel is 11x10-6 K-1, by how much would such a rail change in length between the highest summer temperature (40ºC) and the lowest winter temperature (-40ºC)?

88 cm

The Greenland ice sheet can be one km thick. Estimate the pressure underneath the ice. (The density of ice is 918 kg/m3.)

9.0x10^6 Pa (90 atm)

What is the internal energy of a monatomic gas that has 1.5x1021 particles at a temperature of 310 K?

9.6 J

A stonecutter's chisel has an edge area of 0.50 cm2. If the chisel is struck with a force of 45 N, what is the pressure exerted on the stone?

900 kPa

The sign in the figure weighs 300. N. The boom is of uniform construction. The boom has a mass of 52.0 kg and is 3.20 m in length. The tie cable is attached to the building 2.50 m above the hinge. What is the tension in the tie cable?

901 N

An inventor develops a stationary cycling device by which an individual, while pedaling, can convert all of the energy expended into heat for warming water. How much mechanical energy is required to increase the temperature of 300 g of water (enough for 1 cup of coffee) from 20°C to 95°C? (1 cal = 4.186 J, the specific heat of water is 4.186 J/kg×°C)

94,000 J

The filament temperature of a light bulb is 2,000 K when the bulb delivers 40 W of power. If its emissivity remains constant, what power is delivered when the filament temperature is 2,500 K?

98 W

The force exerted by a stationary liquid on an inclined rectangular surface at rest in the liquid

Acts normally to the surface

When a wool blanket is used to keep warm, what is the primary insulating material?

Air

The noble gases, listed by increasing molecular weight, are He, Ne, Ar, Kr, Xe, and Rn. If samples of 1 mole each of these gases are placed in separate containers and heated to 300 K, which gas has the greatest internal energy and the molecules of which gas have the highest rms speed?

All gasses have the same internal energy, and the He has the greatest rms speed.

Three life preservers have identical volumes. One is filled with Styrofoam. One is filled with sand. One is filled with gravel. When all three are fully submerged under the water, the buoyant force is greatest on the one filled with

All three have the same buoyant force

Two one-liter containers each contain the same number of molecules gas. The temperature is the same in both containers. Container A holds helium (4 particles in the nucleus), and Container B holds argon (40 particles in the nucleus). Which container has the higher pressure and by what factor?

Both containers have the same pressure

Which conservation law governs the Bernoulli's equation?

Conservation of energy

When a substance changes phase, from solid to liquid or liquid to vapor and vice versa, there is no change in temperature, even though heat is being added or removed. Why is there no change in temperature?

During a phase change, energy is used to break/establish the intermolecular bonds rather than stored as kinetic energy of the molecules.

Heat transfer by convection is primarily restricted to

Fluids

Which of the following statements about thermal contact and thermal equilibrium is NOT true?

For energy to be transferred between two objects they have to be in thermal contact.

When an artery gets a constricted region due to plaque, how does the pressure in this region compare to the pressure in an unconstricted region adjacent?

In the constricted region the blood moves at a higher speed than in the constricted region resulting in a decreased pressure

If the temperature on the warmer side of a wall is doubled, the rate at which heat is conducted through the wall is

Increases but the rate cannot be determined

The temperature of a quantity of ideal gas in a sealed container is increased from 0°C to 273°C. What happens to the rms speed of the molecules of the gas as a result of this temperature increase?

It increases but it less than doubles.

Think of Bernoulli's equation as it pertains to an ideal fluid flowing through a horizontal pipe. Imagine that you take measurements along the pipe in the direction of fluid flow. What happens to the sum of the pressure and kinetic energy per unit volume?

It remains constant as the pipe diameter increases

Pennies used to be made of copper, but now they are made of copper-coated zinc. If one were to do a precise calorimetry experiment to determine the specific heat of the new pennies, what would the result be?

It would be between that of copper and that of zinc, depending on coating thickness.

Inside a house, stepping on a tile floor barefooted may feel almost cold, but stepping on carpet in an adjacent room feels comfortably warm. Why is this?

It's because the thermal conductivity of carpet is less than that of tile.

The first experiment, which conclusively demonstrated the equivalence of mechanical energy and heat, was performed by:

Joule

A rock of mass M, that has a density twice that of water, is suspended in water by a thin, massless cord. The tension in the cord is

Mg/2

Which of the following is an assumption that is made in the kinetic theory of gases?

Molecules made up only a small fraction of the volume occupied by a gas.

Which of the following involves the greatest heat transfer?

One gram of steam at 100°C changing to water at 100°C.

7. A container of height, h, is filled with water of density r, and sealed with a flexible membrane. The container is placed in the space shuttle in orbit. If the air pressure in the shuttle is Po, the pressure in the middle of the container is

Po

The star Asthtar is the size of our Sun and at a temperature of 6,000 K, while Procyon is ½ the diameter of our Sun but 12,000 K. Which star is more luminous (that is, a higher power output?

Procyon is more luminous

A loaded ship passes from a lake (fresh water) to the ocean (saltwater). Saltwater is more dense than fresh water and as a result the ship will:

Ride higher in the water

A woman sits on a spinning piano stool with her arms folded. When she extends her arms, which of the following occurs?

She increases her moment of inertia, thereby decreasing her angular speed

Two stars, A and B, have the same emissivity, but the radii and surface temperatures are different with RA = 0.5 RB, and TA = 2 TB. Assuming the temperature of space to be negligible, which star radiates the most energy per unit time?

Star A

If the zeroth law of thermodynamics were not valid, which of the following could not be considered a property of an object?

Temperature

A child standing on the edge of a freely spinning merry-go-round moves quickly to the center. Which one of the following statements is necessarily true concerning this event and why?

The angular speed of the system increases because the moment of inertia of the system has decreased.

A rock is thrown into a swimming pool that is filled with water at a uniform temperature. Which of the following statements is true?

The buoyant force on the rock is constant as it sinks.

Aluminum has a specific heat more than twice that of copper. Identical masses of aluminum and copper, both at 0oC. There are two identical calorimeters. Both calorimeters contain the same volume of water. Both calorimeters are at the same hot temperature. The aluminum mass is dropped into one calorimeter. The copper mass is dropped into the other calorimeter. Both systems come to equilibrium. Compare the equilibrium temperatures of the two masses.

The copper mass has a higher equilibrium temperature than the aluminum mass.

An egg is placed at the bottom of a bowl filled with water. Salt is slowly added to the water until the egg rises and floats. From this experiment, one concludes

The density of salt water exceeds the density of the egg

Two spheres, one with the center core up to r = R/2 hollow and the other solid, have the same mass M and same outer radius R. If they are both rolling at the same linear speed, which one has the greater kinetic energy?

The hollow one has the greater kinetic energy.

Heat is added to a substance at a constant rate. The substance starts as a solid and is melted; the liquid is heated and vaporized; finally, the vapor is heated. This process is shown in the graph. Which of the following statements is correct?

The latent heat of vaporization is greater than the latent heat of fusion.

The inside of a house is at 20°C on an early morning when the temperature outside is 15°C. The next morning the inside temperature is the same but the outside temperature is now 10°C. How much does the energy per unit time lost by conduction through the walls, windows, doors, etc., change for the house from the first morning to the second one?

The loss doubles.

Metal lids on glass jars can often be loosened by running them under hot water. Why is this?

The metal has a higher coefficient of thermal expansion than glass so the metal expands more than the glass thus loosening the connection.

A hurricane strength wind is blowing past a wooden box-shaped shack with its door and windows shut. Which one of the following statements is true?

The one with the smaller volume weighs less than the other

Two objects with different volumes have the same apparent weight when submerged in water. If they are placed in a vacuum,

The one with the smaller volume weighs less than the other

Which of the following is NOT an assumption made in the kinetic theory model of a gas?

The range of molecular forces is much greater than the molecular size.

A spinning star begins to collapse under its own gravitational pull. Which one of the following occurs as the star becomes smaller?

The star's angular momentum remains constant.

Two identical cylindrical discs have a common axis. Initially one of the discs is spinning and the other is at rest. When the two discs are brought into contact, they stick together. Which of the following is true?

The total angular momentum is unchanged, but the total kinetic energy is reduced to half its original value

Thermal energy is added to a solid at 400 K and the temperature of the solid increases to 430 K. What happened to the particles in the solid because of this addition of energy?

They have larger vibrations

Performed the cannon-boring experiment which showed the weakness of the caloric theory.

Thompson, Count Rumford

The reason that buoyant force acts upward on a submerged object is that

Upward pressure against the bottom is greater than the downward pressure against the top of the submerged object

If the angular momentum of a system is constant, which of the following statements must be true?

Zero net torque acts on the system

In a Maxwell-Boltzmann distribution function of molecular speeds, the rms speed is

always greater than the mean speed

A solid cylinder, a hollow cylinder, and a square block of equal masses are released at the top of an inclined plane. The cylinders roll down and the block slides down, all with negligible frictional losses. In what order will they arrive at the bottom?

block, solid cylinder, hollow cylinder

When an object is partly or wholly immersed in a liquid, it is buoyed up

by a force equal to the weight of liquid displaced.

Complete the following statement: When a net torque is applied to a rigid object, it always produces a

change in angular velocity

The use of fiberglass insulation in the outer walls of a building is intended to minimize heat transfer through the wall by what process?

conduction

Which one of the following processes of heat transfer requires the presence of a fluid?

convection

If the thickness of a uniform wall is doubled, the rate at which heat is conducted through the wall is

cut in half

You are floating in a boat in a swimming pool. There are some large stones, with a density of 2.5 g/cm3, in the boat. You throw the stones out of the boat and they sink to the bottom of the pool. The water level h, measured vertically at the end of the pool __________ as the stones are thrown out.

decreases

A large stone is resting on the bottom of the swimming pool. The normal force of the bottom of the pool on the stone is equal to the:

difference between the weight of the stone and the weight of the displaced water.

If the thickness of a uniform wall is halved, the rate at which heat is conducted through the wall is

doubled

To increase the rotational inertia of a solid disk about its axis without changing its mass:

drill holes near the axis and put the material near the rim

Consider two different rods. The greatest thermal conductivity will be in the rod with:

electrons that are freer to move from atom to atom

The specific heat of a substance is a measure of

energy needed to change the kinetic energies of atoms and/or molecules and/or electrons by a temperature increment.

When you are standing your blood pressure is normally greater in your

feet

two types of wall separate a refrigerated room from the rest of a building. Wall 1 has half the thermal conductivity of wall 2. Wall 2 is half as thick as wall 1. The two walls have the same area. The rate of heat flow through wall 2 compared with the rate of heat flow through wall 1 is

four times greater

Lobsters live on the bottom of the ocean. The density of a lobster is

greater than the density of the seawater

The apparent weight of a steel sphere immersed in various liquids is measured using a spring scale. The greatest reading is obtained for that liquid:

having the smallest density

The pressure exerted on the ground by a man is greatest when:

he stands on the toes of one foot

If the absolute temperature of the filament of a lamp were doubled, the energy radiated per second by the filament would

increase by a factor of 16

If cooking is done using an aluminum pan over an electric burner, which of the following will not promote the rate of heat flow from burner to food?

increase pan bottom thickness

A steel plate has a hole drilled through it. The plate is put into a furnace and heated. What happens to the size of the inside diameter of a hole as its temperature increases?

increases

If the absolute temperature of a gas is doubled, what is the change in the average kinetic energy of its molecules?

increases by a factor of 2

If the absolute temperature of an object is tripled, the rate at which it radiates thermal energy

increases by a factor of 81

If the absolute temperature of a gas is doubled, what is the change in the rms speed of its molecules?

increases by a factor of the square root of 2

A disc rotates clockwise in the plane of the page. What is the direction of the angular momentum vector?

into the page

According to Pascal's principle, the pressure at every point in a confined liquid

is changed the same amount by an externally applied pressure.

What happens to its moment of inertia when a steel bar is heated? The axis of rotation is about the center of mass.

it increases

What happens to its moment of inertia when a steel bar is heated? The axis of rotation is about the center of mathe zerothss.

it increases

If a piece of iron is exposed to the sun, its temperature rises until

it loses and gains heat at the same rate.

A balloon is filled with cold air and placed in a warm room. It is NOT in thermal equilibrium with the air of the room until:

it stops expanding

According to Newton's second law, the angular acceleration experienced by an object is inversely proportional to:

its moment of inertia

The oxygen (molar mass = 32 g/mol) and nitrogen (molar mass = 28 g/mol) molecules in this room have equal average

kinetic energies, but the oxygen molecules are slower

The absolute temperature of an ideal gas is directly proportional to which of the following properties, when taken as an average, of the molecules of that gas?

kinetic energy

The temperature of a gas is directly proportional to which of the following properties, when taken as an average, of the molecules of that gas?

kinetic energy

A lobster crawls onto a bathroom scale submerged at the bottom of the ocean. Compared to its weight above the surface, the lobster will have an apparent weight under water that is

less

Heat is added to a substance at a constant rate. The substance starts as a solid and is melted; the liquid is heated and vaporized; finally, the vapor is heated. This process is shown in the graph. The latent heat of fusion can be found by

multiplying the length of B (in seconds) by the rate at which heat is added and dividing by the mass of the substance.

Heat is added to a substance at a constant rate. The substance starts as a solid and is melted; the liquid is heated and vaporized; finally, the vapor is heated. This process is shown in the graph. The latent heat of vaporization can be found by

multiplying the length of D (in seconds) by the rate at which heat is added and dividing by the mass of the substance.

If the sum of the external torques on a system is zero, there is

no change in the systems' angular momentum

6. Which best describes the relationship between two systems in thermal equilibrium?

no net energy is exchanged

A flat plate with a negligible mass and an area of 1.0 cm2 is placed in a horizontal position well beneath the surface in a liquid that is not moving. The pressure at the location of the plate is P Pa. The total force that arises from the pressure of the liquid on this plate is

none of the others

When two gases separated by a diathermal wall are in thermal equilibrium with each other:

only their temperatures must be the same

The buoyant force on an object is least when the object is

partly submerged.

In a stationary homogeneous liquid:

pressure is the same at all points at the same level

You can double both the pressure and the volume of an ideal gas if you change the temperature of the gas by

quadrupling it.

How does the heat energy from the sun reach us through the vacuum of space?

radiation

If one's hands are being warmed by holding them to one side of a flame, the predominant form of heat transfer is

radiation

The earth receives approximately 1.7x1017 J of energy from the sun each second through a process called

radiation

The main process by which heat is transferred to your home when it is heated by solar energy is

radiation

The surfaces of a Dewar flask are silvered for the purpose of minimizing heat transfer by what process?

radiation

Which type of heating causes sunburn?

radiation

John rapidly pulls a plunger out of a cylinder. As the plunger moves away, the gas molecules bouncing elastically off the plunger are:

rebounding at a lower speed than they would have if the plunger weren't removed.

A man turns with an angular velocity on a rotating table, holding two equal masses at arms' length. If he drops the two masses without moving his arms, his angular velocity

remains the same

A person blows across the top of one arm of a U-tube partially filled with water. The water in that arm:

rises slightly

On a sunny day at the beach, the reason the sand gets so hot and the water stays relatively cool is attributed to the difference in which property between water and sand?

specific heat

Sea breezes that occur near the shore are attributed to a difference between land and water with respect to what property?

specific heat

The zeroth law of thermodynamics allows us to define:

temperature

Suppose object C is in thermal equilibrium with object A and with object B. The zeroth law of thermodynamics states:

that A is in thermal equilibrium with B

The Earth's gravity exerts no torque on a satellite orbiting the Earth in an elliptical orbit. Compare the motion of the satellite at the point nearest the Earth (perigee) to the motion at the point farthest from the Earth (apogee). At these two points:

the angular momenta are the same

If the sum of the external torques acting on an isolated system of particles is zero, it must be true that

the angular momentum of the system does not change.

For an ideal gas of a given mass, if the pressure remains the same and the volume increases:

the average kinetic energy of the molecules increases

If the temperature of an ideal gas contained in a rigid box is increased:

the average speed of the molecules in the box will be increased.

When holes are drilled through the wall of a water tower, water will spurt out the greatest horizontal distance from the hole closest to

the bottom of the tower

On a hot summer day, water collects on the outside of a glass of ice lemonade. The water comes from

the condensation of the water vapor due the fact that the glass is much colder than the air.

The reason a life jacket helps you float is

the density of both you and the jacket together is less than your density alone

Which of the following is the mass density of a material?

the material's mass per unit volume

According to Newton's second law, the angular acceleration experienced by an object is directly proportional to:

the net applied torque.

Two uniform circular disks having the same mass and the same thickness are made from different materials. The disk with the smaller rotational inertia is:

the one made from the denser material

A 40-kg boy is standing on the edge of a stationary 30-kg platform that is free to rotate about an ideal frictionless axis. The boy tries to walk around the platform in a counterclockwise direction. As he does:

the platform rotates in a clockwise direction while the boy goes around in a counterclockwise direction relative to the ground

Several cans of different sizes and shapes are all filled with the same liquid to the same depth. Then:

the pressure on the bottom of each can is the same

The angular momentum of a system is conserved only if

the sum of the external torques is zero.

Two identical blocks of ice float in water as shown. Then:

the two blocks displace equal volumes of water since they have the same weight

A horizontal pipe narrows from a diameter of 10 to 5 cm. For a nonviscous fluid flowing from the larger diameter to the smaller,

the velocity increases and the pressure decreases.

The zeroth law of thermodynamics pertains to what relational condition that may exist between two systems?

thermal equilibrium

If two objects are in thermal equilibrium with each other:

they cannot be at different temperatures

If it is known that two bodies are in thermal equilibrium, one can conclude that

they must be at the same temperature

The angular momentum vector for a spinning wheel lies along its axle and is pointed east. To make this vector point south, it is necessary to exert a force on the east end of the axle in which direction?

up

A dam is thicker at the bottom than at the top partly because

water pressure is greater with increasing depth.