Questions and Answers of College Physics A Strategic Approach 2nd

a. Is there a point between a 10 nC charge and a 20 nC charge at which the electric field is zero? If so, which charge is this point closer to? If not, why not? b. Repeat part a for the case of a 10
A rod has positive charge +q at one end and negative charge -q at the other, forming a dipole. The dipole is placed in a nonuniform electric field represented by the field lines in Figure Q20.30.
Storm clouds may build up large negative charges near their bottom edges. The earth is a good conductor, so the charge on the cloud attracts an equal and opposite charge on the earth under the cloud.
A glass bead charged to +3.5 nC exerts an 8.0 × 10-4 N repulsive electric force on a plastic bead 2.9 cm away. What is the charge on the plastic bead? A. +2.1 nC B. +7.4 nC C. +21 nCD. +740 nC
A neutral conducting sphere is between two parallel charged plates, as shown in Figure P20.33. Sketch the electric field lines in the region between the plates. Be sure to include the effect of the
What is the magnitude of the force on the 1.0 nC charge in the middle of Figure P20.49 due to the four other charges? -2.0 nC 1.0 cm 1.0 nC -2.0 nC FIGURE P20.49 -2.0 nC 1.0 cm -2.0 nC
Two equally charged, 1.00 g spheres are placed with 2.00 cm between their centers. When released, each begins to accelerate at 225 m/s2. What is the magnitude of the charge on each sphere?
A 0.020 g plastic bead hangs from a lightweight thread. Another bead is fixed in position beneath the point where the thread is tied. If both beads have charge q, the moveable bead swings out to the
A 5.0 nC point charge sits at x = 0. At the same time, a 4500 N/C uniform electric field (created by distant source charges) points in the positive x-direction. At what point along the x-axis, if
The electron gun in a television tube uses a uniform electric field to accelerate electrons from rest to 5.0 x 107 m/s in a distance of 1.2 cm. What is the electric field strength?
A bead with a mass of 0.050 g and a charge of 15 nC is free to slide on a vertical rod. At the base of the rod is a fixed 10 nC charge. In equilibrium, at what height above the fixed charge does the
A small bead with a positive charge q is free to slide on a horizontal wire of length 4.0 cm. At the left end of the wire is a fixed charge q, and at the right end is a fixed charge 4q. How far from
An "energy bar" contains 6.0 g of fat. How much energy is this in joules? In calories? In Calories?
An "energy bar" contains 22 g of carbohydrates. How much energy is this in joules? In calories? In Calories?
An "energy bar" contains 22 g of carbohydrates. If the energy bar was his only fuel, how far could a 68 kg person walk at 5.0 km/h?
Suppose your body was able to use the chemical energy in gasoline. How far could you pedal a bicycle at 15 km/h on the energy in 1 gal of gas? (1 gal of gas has a mass of 3.2 kg.)
A typical photovoltaic cell delivers 4.0 X 10-3 W of electric energy when illuminated with 1.2 x 10-1 W of light energy. What is the efficiency of the cell?
An individual white LED (light-emitting diode) has an efficiency of 20% and uses 1.0 W of electric power. How many LEDs must be combined into one light source to give a total of 1.6 W of
You're stranded on a remote desert island with only a chicken, a bag of corn, and a shade tree. To survive as long as possible in hopes of being rescued, should you eat the chicken at once and then
A fast-food hamburger (with cheese and bacon) contains 1000 Calories. What is the burger's energy in joules?
For most automobiles, the number of miles per gallon decreases as highway speed increases. Fuel economy drops as speeds increase from 55 to 65 mph, then decreases further as speeds increase to 75
In an average human, basic life processes require energy to be supplied at a steady rate of 100 W. What daily energy intake, in Calories, is required to maintain these basic processes?
When the space shuttle returns to earth, its surfaces get very hot as it passes through the atmosphere at high speed. a. Has the space shuttle been heated? If so, what was the source of the heat? If
A bottle of helium gas and a bottle of argon gas contain equal numbers of atoms at the same temperature. Which bottle, if either, has the greater total thermal energy?
The label on a candy bar says 400 Calories. Assuming a typical efficiency for energy use by the body, if a 60 kg person were to use the energy in this candy bar to climb stairs, how high could she go?
A weightlifter curls a 30 kg bar, raising it each time a distance of 0.60 m. How many times must he repeat this exercise to burn off the energy in one slice of pizza?
A weightlifter works out at the gym each day. Part of her routine is to lie on her back and lift a 40 kg barbell straight up from chest height to full arm extension, a distance of 0.50 m. a. How
The planet Mercury's surface temperature varies from 700 K during the day to 90 K at night. What are these values in °C and °F?
An ideal gas is at 20°C. If we double the average kinetic energy of the gas atoms, what is the new temperature in °C?
An ideal gas is at 20°C. The gas is cooled, reducing the thermal energy by 10%. What is the new temperature in °C?
An ideal gas at °C consists of 1.0 X 1023 atoms. 10 J of thermal energy are added to the gas. What is the new temperature in °C?
An ideal gas at 20°C consists of 2.2 x 1022 atoms. 4.3 J of thermal energy are removed from the gas. What is the new temperature in °C?
In a gasoline engine, fuel vapors are ignited by a spark. In a diesel engine, a fuel-air mixture is drawn in, then rapidly com- pressed to as little as 1/20 the original volume, in the process
600 J of heat energy are transferred to a system that does 400 J of work. By how much does the system's thermal energy change?
1300 J of energy are transferred to a system in the form of heat while the thermal energy increases by 150 J. How much work is done on or by the system?
10 J of heat are removed from a gas sample while it is being compressed by a piston that does 20 J of work. What is the change in the thermal energy of the gas? Does the temperature of the gas
A container holding argon atoms changes temperature by 20°C when 30 J of heat are removed. How many atoms are in the container?
A heat engine with a high-temperature reservoir at 400 K has an efficiency of 0.20. What is the maximum possible temperature of the cold reservoir?
An engine does 10 J of work and exhausts 15 J of waste heat. a. What is the engine's efficiency? b. If the cold-reservoir temperature is 20°C, what is the mini- mum possible temperature in C of
An engine operating at maximum theoretical efficiency whose cold-reservoir temperature is 7°C is 40% efficient. By how much should the temperature of the hot reservoir be increased to raise the
Some heat engines can run on very small temperature differences. One manufacturer claims to have a very small heat engine that can run on the temperature difference between your hand and the air in
An engineer claims to have measured the characteristics of a heat engine that takes in 100 J of thermal energy and produces 50 J of useful work. Is this engine possible? If so, what is the smallest
Each second, a nuclear power plant generates 2000 MJ of thermal energy from nuclear reactions in the reactor's core. This energy is used to boil water and produce high-pressure steam at 300°C. The
250 students sit in an auditorium listening to a physics lecture. Because they are thinking hard, each is using 125 W of metabolic power, slightly more than they would use at rest. An air conditioner
Driving on asphalt roads entails very little rolling resistance, so most of the energy of the engine goes to overcoming air resistance. But driving slowly in dry sand is another story. If a 1500 kg
Air conditioners sold in the United States are given a sea- sonal energy-efficiency ratio (SEER) rating that consumers can use to compare different models. A SEER rating is the ratio of heat pumped
The surface waters of tropical oceans are at a temperature of 27°C while water at a depth of 1200 m is at 3°C. It has been suggested these warm and cold waters could be the energy reservoirs for a
The light energy that falls on a square meter of ground over the course of a typical sunny day is about 20 MJ. The average rate of electric energy consumption in one house is 1.0 kW. a. On average,
Which contains the most moles: 10 g of hydrogen gas, 100 g of carbon, or 50 g of lead?
Which has more mass, a mole of Ne gas or a mole of N2gas?
How many grams of water (H2O) have the same number of oxygen atoms as 1.0 mol of oxygen gas?
If you launch a projectile upward with a high enough speed, its kinetic energy is sufficient to allow it to escape the earth's gravity-it will go up and not come back down. Given enough time,
How many atoms of hydrogen are in 100 g of hydrogen peroxide (H2O2)?
You may have noticed that latex helium balloons tend to shrink rather quickly; a balloon filled with air lasts a lot longer. Bal- loons shrink because gas diffuses out of them. The rate of diffusion
How many cubic millimeters (mm3) are in 1 L?
If you buy a sealed bag of potato chips in Miami and drive with it to Denver, where the atmospheric pressure is lower, you will find that the bag gets very "puffy." Explain why.
A box is 200 cm wide, 40 cm deep, and 3.0 cm high. What is its volume in m?
If you double the typical speed of the molecules in a gas, by what factor does the pressure change? Give a simple explanation why the pressure changes by this factor.
Dry ice is frozen carbon dioxide. If you have 1.0 kg of dry ice, what volume will it occupy if you heat it enough to turn it into a gas at a temperature of 20°C?
Two gases have the same number of molecules per cubic meter (N/V) and the same rms speed. The molecules of gas 2 are more massive than the molecules of gas 1. a. Do the two gases have the same
What is the absolute pressure of the air in your car's tires, in psi, when your pressure gauge indicates they are inflated to 35.0 psi? Assume you are at sea level.
a. Which contains more particles, a mole of helium gas or a mole of oxygen gas? Explain. b. Which contains more particles, a gram of helium gas or a gram of oxygen gas? Explain.
You have 100 g of aluminum and 100 g of lead. a. Which contains a larger number of moles? Explain. b. Which contains more atoms? Explain.
Many cultures around the world still use a simple weapon called a blowgun, a tube with a dart that fits tightly inside. A sharp breath into the end of the tube launches the dart. When exhaling
When you stifle a sneeze, you can damage delicate tissues because the pressure of the air that is not allowed to escape may rise by up to 45 kPa. If this extra pressure acts on the inside of your
A gas cylinder contains 1.0 mol of helium at a temperature of 20°C. A second identical cylinder contains 1.0 mol of neon at 20°C. The helium atoms are moving with a higher average speed, but the
7.5 mol of helium are in a 15 L cylinder. The pressure gauge on the cylinder reads 65 psi. What are (a) The temperature of the gas in °C (b) The average kinetic energy of a helium atom?
Mars has an atmosphere composed almost entirely of carbon dioxide, with an average temperature of -63°C. What is the rms speed of a molecule in Mars's atmosphere?
What is the maximum amount of work that a gas can do during a constant-volume process?
You need to precisely measure the dimensions of a large wood. panel for a construction project. Your metal tape measure was left outside for hours in the sun on a hot summer day, and now the tape is
Your car's radiator is made of steel and is filled with water. You fill the radiator to the very top with cold water, then drive off without remembering to replace the cap. As the water and the steel
A cylinder contains 3.0 L of oxygen at 300 K and 2.4 atm. The gas is heated, causing a piston in the cylinder to move outward. The heating causes the temperature to rise to 600 K and the volume of
Materials A and B have equal densities, but A has a larger specific heat than B. You have 100 g cubes of each material. Cube A, initially at 0°C, is placed in good thermal contact with cube B,
A student is heating chocolate in a pan on the stove. He uses a cooking thermometer to measure the temperature of the chocolate and sees it varies as shown in Figure Q12.20. Describe what is
A sample of ideal gas is in a cylinder with a movable piston. 600 J of heat is added to the gas in an isothermal process. As the gas expands, pushing against the piston, how much work does it do?
If you bake a cake at high elevation, where atmospheric pressure is lower than at sea level, you will need to adjust the recipe. You will need to cook the cake for a longer time, and you will need to
The specific heat of aluminum is higher than that of iron. 1 kg blocks of iron and aluminum are heated to 100°C, and each is then dropped into its own 1 L beaker of 20°C water. Which beaker will
If you have two spoons of the same size, one silver and one stainless steel, there is a quick test to tell which is which. Hold the end of a spoon in each hand, then lower them both into a cup of
It is possible to make a thermometer by scaling gas in a rigid container and measuring the absolute pressure. Such a constant- volume gas thermometer is placed in an ice-water bath at 0.00°C. After
If you live somewhere with cold, clear nights, you may have noticed some mornings when there was frost on open patches of ground but not under trees. This is because the ground under trees does not
A 1.0 cm3 air bubble is released from the sandy bottom of a warm, shallow sea, where the gauge pressure is 1.5 atm. The bubble rises slowly enough that the air inside remains at the same constant
A tire is inflated to a gauge pressure of 35 psi. The absolute pressure in the tire is A. Less than 35 psi. B. Equal to 35 psi. C. Greater than 35 psi.
A weather balloon rises through the atmosphere, its volume expanding from 4.0 m3 to 12 m3 as the temperature drops from 20°C to -10°C. If the initial gas pressure inside the balloon is 1.0 atm,
The number of atoms in a container is increased by a factor of 2 while the temperature is held constant. The pressure A. Decreases by a factor of 4. B. Decreases by a factor of 2. C. Stays the
A straight rod consists of a 1.2-cm-long piece of aluminum attached to a 2.0-cm-long piece of steel. By how much will the length of this rod change if its temperature is increased from 20°C to 40°C?
A gas is compressed by an isothermal process that decreases its volume by a factor of 2. In this process, the pressure.A. Does not change. B. Increases by a factor of less than 2. C. Increases by a
The length of a steel beam increases by 0.73 mm when its temperature is raised from 22°C to 35°C. What is the length of the beam at 22°C?
A gas is compressed by an adiabatic process that decreases its volume by a factor of 2. In this process, the pressure A. Does not change. B. Increases by a factor of less than 2. C. Increases by a
Older railroad tracks in the U.S. are made of 12-m-long pieces of steel. When the tracks are laid, gaps are left between the sections to prevent buckling when the steel thermally expands. If a track
Suppose you do a calorimetry experiment to measure the specific heat of a penny. You take a number of pennies, measure their mass, heat them to a known temperature, and then drop them into a
The temperature of an aluminum disk is increased by 120°C. By what percentage does its volume increase?
A cup of water is heated with a heating coil that delivers 100 W of heat. In one minute, the temperature of the water rises by 20°C. What is the mass of the water? A. 72 g C. 720 g B. 140 g D. 1.4 kg
How much energy must be removed from a 200 g block of ice to cool it from 0°C to -30°C?
100 g of ice at 0°C and 100 g of steam at 100°C interact thermally in a well-insulated container. The final state of the system isA. An ice-water mixture at 0°C. B. Water at a temperature between
Suppose the 600 W of radiation emitted in a microwave oven is absorbed by 250 g of water in a very lightweight cup. Approximately how long will it take to heat the water from 20°C to 80°C?A.
The maximum amount of water an adult in temperate climates can perspire in one hour is typically 1.8 L. However, after several weeks in a tropical climate the body can adapt, increasing the maximum
Alligators and other reptiles don't use enough metabolic energy to keep their body temperatures constant. They cool off at night and must warm up in the sun in the morning. Suppose a 300 kg alligator
When air is inhaled, it quickly becomes saturated with water vapor as it passes through the moist upper airways. When breathing dry air, about 25 mg of water are exhaled with each breath. At 12
It is important for the body to have mechanisms to effectively cool itself; if not, moderate exercise could easily increase body temperatures to dangerous levels. Suppose a 70 kg man runs on a
What minimum heat is needed to bring 100 g of water at 20°C to the boiling point and completely boil it away?

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