Physics 101 Final

The Aswan High Dam on the Nile River in Egypt is 111 m high. What is the gauge pressure in the water at the foot of the dam? The density of water is 1000 kg/m3.

1.09 × 10^6 Pa

A 10-kg mass, hung by an ideal spring, causes the spring to stretch 2.0 cm. What is the spring constant (force constant) for this spring?

49 N/cm

The coefficient of linear expansion for aluminum is 1.8 × 10-6 K-1. What is its coefficient of volume expansion?

5.4 × 10^-6 K-1

A vertical 30-cm steel rod, 1.0 cm in diameter, supports a 300-kg mass. What is the change in length of the rod caused by this mass? Young's modulus for steel is 2.0 × 1011 N/m2.

5.6 × 10^-5 m

A solid cylindrical bar conducts heat at a rate of 25 W from a hot to a cold reservoir under steady state conditions. If both the length and the diameter of this bar are doubled, the rate at which it will conduct heat between these reservoirs will be

50 W

What buoyant force does a 0.60-kg solid gold crown experience when it is immersed in water? The density of gold is 19.3 × 103 kg/m3 and that of water is 1000 kg/m3.

0.30 N

A 0.140-kg baseball is dropped and reaches a speed of 1.20 m/s just before it hits the ground and bounces. It rebounds with an upward velocity of 1.00 m/s. What is the change of the ball's momentum during the bounce?

0.308 kg m/s upwards

What is the kinetic energy of a 120-cm thin uniform rod with a mass of 450 g that is rotating about its center at 3.60 rad/s?

0.350 J

A brass wire 2.0 m long and 2.0 mm in diameter supports a 10.0-kg fixture. By what distance did this fixture stretch the wire? Young's modulus for brass is 10 × 1010 N/m2.

0.62 mm

When a fan is turned off, its angular speed decreases from 10 rad/s to 6.3 rad/s in 5.0 s. What is the magnitude of the average angular acceleration of the fan?

0.74 rad/s2

Which two temperature changes are equivalent?

1 C° = 1 K

An ice skater has a moment of inertia of 5.0 kg m2 when her arms are outstretched, and at this time she is spinning at 3.0 rev/s. If she pulls in her arms and decreases her moment of inertia to 2.0 kg m2, how fast will she be spinning?

7.5 rev/s

A carpenter is driving a 15.0-g steel nail into a board. His 1.00-kg hammer is moving at 8.50 m/s when it strikes the nail. Half of the kinetic energy of the hammer is transformed into heat in the nail and does not flow out of the nail. What is the increase in temperature of the nail after the three blows that the carpenter needs to drive the nail in completely? The specific heat of steel is 448 J/kg K.

8.1 K

A heat-conducting rod that is wrapped in insulation is constructed with a 0.15-m length of alloy A and a 0.40-m length of alloy B, joined end-to-end. Both pieces have cross-sectional areas of 0.0020 m2. The thermal conductivity of alloy B is known to be 1.8 times as great as that for alloy A. The end of the rod in alloy A is maintained at a temperature of 10°C, and the other end of the rod is maintained at an unknown temperature. When steady state flow has been established, the temperature at the junction of the alloys is measured to be 40° C, and the rate of heat flow in the rod is measured at 56 W. What is the temperature of the end of the rod in alloy B?

84°C

Two friends are standing on opposite ends of a canoe that is initially at rest with respect to a frictionless lake. The person in the front throws a very massive ball toward the back, and the person in the back catches it. After the ball is caught, the canoe is

stationary.

Two objects of different masses have momentum of equal, non-zero magnitude. Which object has more kinetic energy?

the lighter object

A merry-go-round spins freely when Diego moves quickly to the center along a radius of the merry-go-round. As he does this, it is true to say that

the moment of inertia of the system decreases and the angular speed increases.

As one stretches a metal wire, which condition is reached first?

the proportional limit

A small uniform disk and a small uniform sphere are released simultaneously at the top of a high inclined plane, and they roll down without slipping. Which one will reach the bottom first?

the sphere

When a car is weighed, it is driven slowly on a horizontal floor over a scale that records a reading as the front wheels go over the scale, and then records a second reading as the rear wheels go over the scale. The weight of the car is equal to You Answered

the sum of the two weights.

Two metal spheres are made of the same material and have the same diameter, but one is solid and the other is hollow. If their temperature is increased by the same amount,

the two spheres remain of equal size.

On a cold day, a piece of metal feels much colder to the touch than a piece of wood. This is due to the difference in which one of the following physical properties of these materials?

thermal conductivity

A typical incandescent light bulb consumes 75 W of power and has a mass of 30 g. You want to save electrical energy by dropping the bulb from a height great enough so that the kinetic energy of the bulb when it reaches the floor will be the same as the energy it took to keep the bulb on for 1.0 hour. From what height should you drop the bulb, assuming no air resistance and constant g?

920 km

A 1-kg ball is released from a height of 6 m, and a 2-kg ball is released from a height of 3 m. Air resistance is negligible as they fall. Which of the following statements about these balls are correct? (There could be more than one correct choice.)

As they reach the ground, the 1-kg ball will be moving faster than the 2-kg ball. Both balls will reach the ground with the same kinetic energy.

Water flows through a pipe. The diameter of the pipe at point B is larger than at point A. Where is the water pressure greatest?

at point B

The process in which heat flows by the mass movement of molecules from one place to another is known as

convection.

Which one of the following is an accurate statement?

The ratio of tensile stress to tensile strain is called Young's modulus.

Identical forces act for the same length of time on two different objects. The magnitude of the change in momentum of the lighter object is

exactly equal to the magnitude of the change in momentum of the larger mass.

At what, if any, temperature are the numerical readings on the Fahrenheit and Celsius scales the same?

-40°

The coefficient of linear expansion of aluminum is 24 × 10-6 K-1 and the coefficient of volume expansion of olive oil is 0.68 × 10-3 K-1. A novice cook, in preparation of some pesto, fills a 1.00-L aluminum pot to the brim and heats the oil and the pot from an initial temperature of 15°C to 190°C. To his consternation some olive oil spills over the top. How much?

0.11 L

To determine the location of the center of mass (or center of gravity) of a car, the car is driven over a scale on a horizontal floor. When the front wheels are over the scale, the weight recorded by the scale is 5800 N, and when the rear wheels are over the scale, the scale reads 6500 N. The distance between the front and rear wheels is measured to be 3.20 m. How far behind the front wheels is the center of mass located?

1.69 m

When a container of water is placed on a laboratory scale, the scale reads 120 g. Now a 20-g piece of copper (of density 8.9 g/cm3) is suspended from a thread and lowered into the water, not touching the bottom of the container. What will the scale now read? The density of water is 1.0 g/cm3.

122 g

At room temperature, a typical person loses energy to the surroundings at the rate of 62 W. If this energy loss has to be made up by an equivalent food intake, how many kilocalories (food calories) does this person need to consume every day just to make up this heat loss? (1 cal = 4.186 J)

1300 kcal

An object having a fixed emissivity of 0.725 radiates heat at a rate of 10 W when it is at an absolute temperature T. If its temperature is doubled to 2T, at what rate will it now radiate?

160 W

A 600-kg car makes a 90° turn. Its speed before the turn is 21.0 m/s and after the turn it is 24.0 m/s. What is the magnitude of the change in the car's momentum during the turn?

19.1 × 10^3 kgm/s

A 12-L volume of oil is subjected to pressure which produces a volume strain of -3.0 × 10-4. The bulk modulus of the oil is 6.0 × 109 Pa and is independent of the pressure. The reduction in the volume of the oil in milliliters is closest to

3.6 mL.

A 2.0-kg mass moving at 5.0 m/s suddenly collides head-on with a 3.0-kg mass at rest. If the collision is perfectly inelastic, what is the speed of the masses just after the collision?

2.0 m/s

An Atwood machine consists of a mass of 3.5 kg connected by a light string to a mass of 6.0 kg over a frictionless pulley with a moment of inertia of 0.0352 kg m2 and a radius of 12.5 cm. If the system is released from rest, what is the speed of the masses after they have moved through 1.25 m if the string does not slip on the pulley?

2.3 m/s

A firecracker breaks up into two pieces, one of which has a mass of 200 g and flies off along the +x-axis with a speed of 82.0 m/s. The second piece has a mass of 300 g and flies off along the +y-axis with a speed of 45.0 m/s. What is the total momentum of the two pieces?

21.2 kg m/s at 39.5° from the +x-axis

A dinner plate falls vertically to the floor and breaks up into three pieces, which slide horizontally along the floor. Immediately after the impact, a 320-g piece moves along the +x-axis with a speed of 2.00 m/s and a 355-g piece moves along the +y-axis with a speed of 1.50 m/s. The third piece has a mass of 100 g. In what direction relative to the +x-axis does the third piece move?

219.8° from the +x-axis

Two uniform solid spheres have the same mass, but one has twice the radius of the other. The ratio of the larger sphere's moment of inertia about a central axis to that of the smaller sphere is

4.

How much heat is required to raise the temperature of a 225-g lead ball from 15.0°C to 25.0°C? The specific heat of lead is 128 J/kg K.

288 J

An ideal gas is held in a container of volume V at pressure p. The rms speed of a gas molecule under these conditions is v. If now the volume and pressure are changed to 2V and 2p, the rms speed of a molecule will be

2v

An ideal incompressible fluid flows at 12 m/s in a horizontal pipe. If the pipe widens to twice its original radius, what is the flow speed in the wider section?

3.0 m/s

A person tries to heat up her bath water by adding 5.0 L of water at 80°C to 60 L of water at 30°C. What is the final temperature of the bath water?

34°C

A 4.7-kg solid sphere, made of metal whose density is 4000 kg/m3, hangs by a light cord. When the sphere is immersed in water, what is the tension in the cord? The density of water is 1000 kg/m3.

35 N

A small 1.4-N stone slides down a frictionless bowl, starting from rest at the rim. The bowl itself is a hemisphere of radius 75 cm. Just as the stone reaches the bottom of the bowl, how hard is the bowl pushing on it?

4.2 N

A sand mover at a quarry lifts 2,000 kg of sand per minute a vertical distance of 12 m. The sand is initially at rest and is discharged at the top of the sand mover with speed 5.0 m/s into a loading chute. What minimum power must be supplied to this machine?

4.3 kW

A 5.00-m-long uniform ladder, weighing 200 N, rests against a smooth vertical wall with its base on a horizontal rough floor, a distance of 1.20 m away from the wall. The coefficient of static friction between the ladder and the floor is 0.200. How far up the ladder, measured along the ladder, can a 600-N person climb before the ladder begins to slip?

4.56 m

A sealed cylinder fitted with a movable piston contains ideal gas at 27°C, pressure 0.500 × 105 Pa, and volume 1.25 m3. What will be the final temperature if the gas is compressed to 0.800 m3 and the pressure rises to 0.820 × 105 Pa?

42°C

A sealed container holds 0.020 moles of ideal nitrogen (N2) gas, at a pressure of 1.5 atm and a temperature of 290 K. The atomic mass of nitrogen is 14.0 g/mol. What is the average translational kinetic energy of a nitrogen molecule? The Boltzmann constant is 1.38 × 10-23 J/K.

6.0 ×10^21 J

A rock falls from a vertical cliff that is 4.0 m tall and experiences no significant air resistance as it falls. At what speed will its gravitational potential energy (relative to the base of the cliff) be equal to its kinetic energy?

6.3 m/s

The rms speed of a certain sample of carbon dioxide molecules, with a molecular weight of 44.0 g/mole, is 396 m/s. What is the rms speed of water vapor molecules, with a molecular weight of 18.0 g/mol, at the same temperature as the carbon dioxide?

619 m/s

Two identical grasshoppers jump into the air with the same initial speed and experience no air resistance. Grasshopper A goes straight up, but grasshopper B goes up at a 66° angle above the horizontal. Which of the following statements about these grasshoppers are correct? (There could be more than one correct choice.)

At their highest point, both of them have the same amount of mechanical energy. At their highest point, grasshopper B is moving faster than grasshopper A. At their highest point, grasshopper A has more gravitational potential energy than grasshopper B.

Consider a uniform hoop of radius R and mass M rolling without slipping. Which is larger, its translational kinetic energy or its rotational kinetic energy?

Both are equal.

You and your friend, who weighs the same as you, want to go to the top of the Eiffel Tower. Your friend takes the elevator straight up. You decide to walk up the spiral stairway, taking longer to do so. Compare the gravitational potential energy of you and your friend, after you both reach the top.

Both of you have the same amount of gravitational potential energy at the top.

A piece of iron rests on top of a piece of wood floating in a bathtub. If the iron is removed from the wood, and kept out of the water, what happens to the water level in the tub?

It goes down.

A piece of iron sinks to the bottom of a lake where the pressure is 21 times what it is at the surface. Which statement best describes what happens to the density of that piece of iron?

Its density increases slightly.

A piece of iron sinks to the bottom of a lake where the pressure is 21 times what it is at the surface of the lake. Which statement best describes what happens to the volume of that piece of iron?

Its volume decreases slightly.

As a rock sinks deeper and deeper into water of constant density, what happens to the buoyant force on it if it started above the surface of the water?

The buoyant force first increases and then remains constant.

A spherical ball of lead (density 11.3 g/cm3) is placed in a tub of mercury (density 13.6 g/cm3). Which answer best describes the result?

The lead ball will float with about 17% of its volume above the surface of the mercury.

You throw a baseball straight up. Compare the sign of the work done by gravity while the ball goes up with the sign of the work done by gravity while it goes down.

The work is negative on the way up and positive on the way down.

Three cars, car X, car Y, and car Z, begin accelerating from rest at the same time. Car X is more massive than car Y, which is more massive than car Z. The net accelerating force exerted on each car is identical. After 10 seconds, which car has the most amount of momentum?

They all have the same amount of momentum.

When a rigid object rotates about a fixed axis, what is true about all the points in the object? (There could be more than one correct choice.)

They all have the same angular speed. They all have the same angular acceleration.

Three cars (car F, car G, and car H) are moving with the same speed and slam on their brakes. The most massive car is car F, and the least massive is car H. If the tires of all three cars have identical coefficients of kinetic friction with the road surface, which car travels the longest distance to skid to a stop?

They all travel the same distance in stopping.

A ballet dancer is spinning in the middle of a horizontal frictionless stage. Which of the following things could he change by moving parts of his body or his whole body? (There could be more than one correct choice.)

his total kinetic energy his translational kinetic energy his rotational kinetic energy his angular momentum his moment of inertia the location of his center of mass (or center of gravity)

Oxygen molecules are 16 times more massive than hydrogen molecules. At a given temperature, the average molecular kinetic energy of oxygen molecules, compared to that of hydrogen molecules,

is the same.

Which one of the following quantities is the smallest unit of heat energy?

joule

Salt water is denser than fresh water. A ship floats in both fresh water and salt water. Compared to the fresh water, the volume of water displaced in the salt water is

less.

An egg falls from a bird's nest in a tree and feels no effects due to the air. As it falls,

only its mechanical energy is conserved.