Are entropy changes always caused by the flow of heat? If not, give some other examples of processes that increase entropy.
> Color printers always use at least three different colors of ink or toner. Televisions and computer monitors have pixels of at least three different colors. Why are at least three necessary? [Hint: See Fig. 24.9.]
> Sheena can row a boat at 3.00 mi/h in still water. She needs to cross a river that is 1.20 mi wide with a current flowing at 1.60 mi/h. Not having her calculator ready, she guesses that to go straight across, she should head upstream at an angle of 25.0°
> A circular metal loop carries a current I as shown. The points are all in the plane of the page and the loop is perpendicular to the page. Sketch the loop, and draw vector arrows at the points A, B, C, D, and E to show the direction of the magnetic field
> Finola has a circuit with a 4.00 kΩ resistor, a 0.750 H inductor, and a capacitor of unknown value connected in series to a 440.0 Hz ac source. With an oscilloscope, she measures the phase angle to be 25.0°. (a) What is the value of the unknown capacito
> At a point due south of the transmitter, what is the direction of the wave’s magnetic field?
> A constant force, acting for 3.6 × 104 s (10 h), brings a spaceship of mass 2200 kg from rest to speed 0.70c. (a) What is the magnitude of the force? [Hint: Use the impulse-momentum theorem.] (b) What is the initial acceleration of the spaceship? Comme
> Why does a mirror hanging in a vertical plane seem to interchange left and right but not up and down? [Hint: Refer to Fig. 23.28. Instead of calling Grant's hands left and right, call them east and west. In Grant's image, are the east and west hands reve
> A transverse wave on a string is described by Plot the displacement y and the velocity vy versus t for one complete cycle of the point x = 0 on the string.
> Point P is at a potential of 500.0 kV, and point S is at a potential of 200.0 kV. The space between these points is evacuated. When a charge of +2e moves from P to S, by how much does its kinetic energy change?
> How much work is done by an applied force that moves two charges of 6.5 µC that are initially very far apart to a distance of 4.5 cm apart?
> If a uniform electric field exists in a region of space, is the potential the same at all points in the region? Explain.
> We can model some of the electrical properties of an unmyelinated axon as an electric cable covered with defective insulation so that current leaks out of the axon to the surrounding fluid. We assume the axon consists of a cylindrical membrane filled wit
> Four masses are arranged as shown. They are connected by rigid, massless rods of lengths 0.75 m and 0.50 m. What torque must be applied to cause an angular acceleration of 0.75 rad/s2 about the axis shown?
> (a) When ice floats in water at 0°C, what percent of its volume is submerged? (b) What is the specific gravity of ice?
> At a rock concert, the engineer decides that the music isn't loud enough. He turns up the amplifiers so that the amplitude of the sound, where you're sitting, increases by 50.0%. (a) By what percentage does the intensity increase? (b) How does the inte
> In a velocity selector, the electric and magnetic forces cancel if . Show that / must be in the same direction as / [Hint: Since is perpendicular to both and in a velocity selector, there are only two possibilities for the direction of /:
> A circular conducting loop with radius 3.40 cm is placed in a uniform magnetic field of 0.880 T with the plane of the loop perpendicular to the magnetic field, as shown. The loop is rotated 180° about the axis in 0.222 s. (a) As the loop begi
> Dash is standing on his frictionless skateboard with three balls, each with a mass of 100 g, in his hands. The combined mass of Dash and his skateboard is 60 kg. How fast should Dash throw the balls forward if he wants to move backward with a speed of 0.
> How many different hadrons are stable (as far as we know)?
> According to Maxwell, why is it impossible to have an electric wave without any magnetic component?
> Find the energy for a hydrogen atom in the stationary state n = 4.
> Stan and Ollie are standing next to a train track. Stan puts his ear to the steel track to hear the train coming. He hears the sound of the train whistle through the track 2.1 s before Ollie hears it through the air. How far away is the train?
> A stretched string has a fundamental frequency of 847 Hz. What is the fundamental frequency if the tension is increased by a factor of 3.0?
> You are bicycling along a straight north-south road. Let the x-axis point north. Describe your motion in each of the following cases. Example: ax > 0 and vx > 0 means you are moving north and speeding up. (a) ax > 0 and vx < 0. (b) ax = 0 and vx < 0.
> Under what special circumstances can kelvins or Celsius degrees be used interchangeably?
> At a point P, a distance R0 from a positive charge Q0, the electric field has a magnitude E0 = 100 N/C and the electric potential is V0 = 10 V. The charge is now increased by a factor of three, becoming 3Q0. (a) At what distance, RE, from the charge 3Q0
> An electroscope consists of a conducting sphere, conducting pole, and two metal foils (see Fig. 16.10). The electroscope is initially uncharged. (a) A positively charged rod is allowed to touch the conducting sphere and then is removed. What happens to
> The eyepiece of a Galilean telescope is a diverging lens. The focal points Fo and F′e coincide. In one such telescope, the lenses are a distance d = 32 cm apart and the focal length of the objective is 36 cm. A rhinoceros is viewed from
> An RC filter is shown. The filter resistance R is variable between 180 Ω and 2200 Ω and the filter capacitance is C = 0.086 µF. At what frequency is the output amplitude equal to times the input amplitude if R = (a
> A radio wave with a wavelength of 1200 m follows two paths to a receiver that is 25.0 km away. One path goes directly to the receiver and the other reflects from an airplane that is flying above the point that is exactly halfway between the transmitter a
> In tall buildings, the water supply system uses multiple pumping stations on different floors. At each station, water pumped up from below collects in a storage tank held at atmospheric pressure before it enters the pump. The storage tank supplies water
> A truck carrying explosive gases either has chains or straps that drag along the ground, or else it has special tires that conduct electricity (ordinary tires are good insulators). Explain why the chains, straps, or conducting tires are necessary.
> You are given two x-ray tubes, A and B. In tube A, electrons are accelerated through a potential difference of 10 kV. In tube B, the electrons are accelerated through 40 kV. What is the ratio of the minimum wavelength of x-rays in tube A to the minimum w
> Explain why electric field lines never cross.
> A fellow student says that there is never an electric field inside a conductor. Do you agree? Explain.
> Two strings, each 15.0 m long, are stretched side by side. One string has a mass of 78.0 g and a tension of 180.0 N. The second string has a mass of 58.0 g and a tension of 160.0 N. A pulse is generated at one end of each string simultaneously. (a) On w
> (a) What is the density of an object that is 14% submerged when floating in water at 0°C? (b) What percentage of the object will be submerged if it is placed in ethanol at 0°C?
> The speed of waves on a lake depends on frequency. For waves of frequency 1.0 Hz, the wave speed is 1.56 m/s; for 2.0 Hz waves, the speed is 0.78 m/s. The 2.0 Hz waves from a speedboat's wake reach you 120 s after the 1.0 Hz waves generated by the same b
> Simon wishes to display a double-slit experiment for his class. His coherent light source has a wavelength of 510 nm, and the slit separation is d = 0.032 mm. He must set up the light on a desk 1.5 m away from the screen that is only 10 cm wide. How many
> Bruce is trying to remove an eyelash from the surface of his eye. He looks in a shaving mirror to locate the eyelash, which is 0.40 cm long. If the focal length of the mirror is 18 cm and he puts his eye at a distance of 11 cm from the mirror, how long i
> An electric device has the current-voltage (I-V) graph shown. What is its resistance at (a) point 1 and (b) point 2? [Hint: Use the definition of resistance.]
> When the muscles of the eye remain tensed for a significant period of time, eyestrain results. How much is this a concern for a person using (a) a microscope, (b) a telescope, and (c) a simple magnifier?
> The instantaneous sinusoidal emf from an ac generator with an rms emf of 4.0 V oscillates between what values?
> The K0 meson can decay to two pions: K0 → π+ + π−. The rest energies of the particles are: K0 = 497.7 MeV, π+ = π− = 139.6 MeV. If the K0 is at rest before it decays, what are the kinetic energies of the π+ and the π− after the decay?
> The length of a spring increases by 7.2 cm from its relaxed length when a mass of 1.4 kg is hanging in equilibrium from the spring. (a) What is the spring constant? (b) How much elastic potential energy is stored in the spring? (c) A different mass is
> Due to the similarity between Newton’s law of gravity and Coulomb’s law, a friend proposes this hypothesis: perhaps there is no gravitational interaction at all. Instead, what we call gravity might be electric forces acting between objects that are almos
> An airplane is flying at constant speed 740 km/h in a horizontal circle of radius 4.1 km. The lift force on the wings due to the air is perpendicular to the wings. At what angle to the vertical must the wings be banked to fly in this circle?
> While an elevator of mass 832 kg moves downward, the tension in the supporting cable is a constant 7730 N. Between t = 0 and t = 4.00 s, the elevator's displacement is 5.00 m downward. What is the elevator's speed at t = 4.00 s?
> A Compton scattering experiment is performed using an aluminum target. The incident photons have wavelength λ. The scattered photons have wavelengths λ′ and energies E that depend on the scattering angle θ. (a) At what angle θ are scattered photons with
> Why are heat pumps more often used in mild climates than in areas with severely cold winters?
> The pull cord of a lawnmower engine is wound around a drum of radius 6.00 cm. While the cord is pulled with a force of 75 N to start the engine, what magnitude torque does the cord apply to the drum?
> A discus thrower moves the discus in 1.5 complete revolutions in 1.4 s (starting from rest). The radius of the circular path of the discus is 0.90 m, and the mass of the discus is 2.0 kg. Assume a constant torque is applied to the discus by the athlete.
> Two spaceships are observed from Earth to be approaching each other along a straight line. Ship A moves at 0.40c relative to the Earth observer, and ship B moves at 0.50c relative to the same observer. What speed does the captain of ship A report for the
> Two steel wires (of the same length and different radii) are connected together, end to end, and tied to a wall. An applied force stretches the combination by 1.0 mm. How far does the midpoint move?
> A 2010 kg elevator moves with an upward acceleration of 1.50 m/s2. What is the tension in the cable that supports the elevator?
> Rank the flywheels in order of the linear speed at the rim, largest to smallest. Explain.
> No currents flow in the circuit diagrammed before the switch is closed. Consider all the circuit elements to be ideal. (a) At the instant the switch is closed, what are the values of the currents I1 and I2, the potential differences across the resistors
> Two blocks, one with mass m1 = 0.050 kg and one with mass m2 = 0.030 kg, are connected to each other by a string. The inner block is connected to a central pole by another string as shown in the figure with r1 = 0.40 m and r2 = 0.75 m. When the blocks ar
> A television set draws an rms current of 2.50 A from a 60 Hz power line. Find (a) the average current, (b) the average of the square of the current, and (c) the amplitude of the current.
> In everyday experience, visible light seems to travel in straight lines whereas radio waves do not. Explain.
> A proton is initially at rest and moves through three different regions as shown in the figure. In region 1, the proton accelerates across a potential difference of 3330 V. In region 2, there is a magnetic field of 1.20 T pointing out of the page and an
> A block of mass 2.00 kg slides eastward along a frictionless surface with a speed of 2.70 m/s. A chunk of clay with a mass of 1.50 kg slides southward on the same surface with a speed of 3.20 m/s. The two objects collide and move off together. What is th
> Most heat pumps incorporate an auxiliary electric heater. For relatively mild outdoor temperatures, the electric heater is not used. However, if the outdoor temperature gets very low, the auxiliary heater is used to supplement the heat pump. Why?
> When snorkeling, you wear goggles in order to see clearly. Why is your vision blurry without the goggles? A nearsighted person notices that he is able to see more clearly when he is underwater (without goggles or corrective lenses) than in air (without c
> The Milky Way galaxy rotates about its center with a period of about 200 million yr. The Sun is 2 × 1020 m from the center of the galaxy. (a) What is the Sun’s radial acceleration? (b) What is the net gravitational force on the Sun due to the other star
> The graph shows the force exerted on an object versus the position of that object along the x-axis. The force has no components other than along the x-axis. What is the work done by the force on the object as the object is displaced from 0 to 3.0 m?
> Table 12.2 lists 120 dB as the intensity level at the threshold of pain for humans. (a) Show that the corresponding pressure amplitude is 29 Pa. (b) What is this pressure amplitude as a fraction of atmospheric pressure?
> A block is released from rest and slides down an incline. The coefficient of sliding friction is 0.38, and the angle of inclination is 60.0°. (a) Use energy considerations to find how fast the block is sliding after it has traveled a distance of 30.0 cm
> If you leave the refrigerator door open and the refrigerator runs continuously, does the kitchen get colder or warmer? Explain.
> A transverse wave on a string is described by Sketch graphs of the transverse velocity and acceleration of the point x = 0 as functions of time, showing one complete cycle.
> What are the advantages of using hydraulic systems rather than mechanical systems to operate automobile brakes or the control surfaces of an airplane?
> Two African swallows fly toward each other, carrying coconuts. The first swallow is flying north horizontally with a speed of 20 m/s. The second swallow is flying at the same height as the first and in the opposite direction with a speed of 15 m/s. The m
> Some electric appliances are able to operate equally well with either dc or ac voltage sources, but other appliances require one type of source or the other and cannot run on both. Explain and give a few examples of each type of appliance.
> The graph shows vx in meters per second versus t in seconds for a skateboard moving along the x-axis. How far does the board move between t = 3.00 s and t = 8.00 s? Sketch a motion diagram and a graph of x(t) for the same time interval.
> A centrifuge has a rotational inertia of 6.5 × 10−3 kg·m2. How much energy must be supplied to bring it from rest to 420 rad/s (4000 rev/min)?
> When a block of ebony is placed in ethanol, what percentage of its volume is submerged?
> Consider the emission spectrum of singly ionized helium (He+). Find the longest three wavelengths for the series in which the electron makes a transition from a higher excited state to the first excited state (not the ground state).
> A bicycle is moving at 9.0 m/s. What is the angular speed of its tires if their radius is 35 cm?
> Show that the spontaneous alpha decay of 19O is not possible.
> A 4.0 N object is attached to the bottom of an ideal spring of spring constant 250 N/m. The spring is initially in its relaxed position. Write an equation to describe the motion of the object if it is released at t = 0. [Hint: Let y = 0 at the equilibri
> When supplies of fossil fuels such as petroleum and coal dwindle, people might call the situation an “energy crisis.” From the standpoint of physics, why is that not an accurate name? Can you think of a better one?
> A person in bare feet is standing under a tree during a thunderstorm, seeking shelter from the rain. A lightning strike hits the tree. A burst of current lasting 40 µs passes through the ground; during this time the potential difference between his feet
> In Section 22.3, we stated that an electric dipole antenna should be aligned with the electric field of an EM wave for best reception. If a magnetic dipole antenna is used instead, should its axis be aligned with the magnetic field of the wave? Explain.
> Find the magnetic field at point R, the midpoint of the left side of the square.
> By what percentage does the density of water increase at a depth of 1.0 km below the surface?
> Why must all reversible engines (operating between the same reservoirs) have the same efficiency? Try an argument by contradiction: imagine that two reversible engines exist with e1 > e2. Reverse one of them (into a heat pump) and use the work output fro
> A ball of mass 0.10 kg moving with speed of 2.0 m/s hits a wall and bounces back with the same speed in the opposite direction. What is the change in the ball’s kinetic energy?
> Would a ground fault interrupter work if the circuit used dc current instead of ac? Explain.
> A cylindrical steel bar is compressed by the application of forces of magnitude F at each end. What magnitude forces would be required to compress by the same amount (a) a steel bar of the same cross- sectional area but one half the length? (b) a steel
> A car drives around a curve with radius 410 m at a speed of 32 m/s. The road is not banked. The mass of the car is 1400 kg. (a) What is the frictional force on the car? (b) Does the frictional force necessarily have magnitude μsN? Explain.
> Why is a refracting telescope with a large angular magnification longer than one with a smaller magnification?
> An electron with a velocity of 10.0 m/s in the positive y-direction enters a region where there is a uniform electric field of 200 N/C in the positive x-direction. What are the x- and y-components of the electron’s displacement 2.40 &Ac
> In the crossover network of Problem 63, the inductance L is 1.20 mH. The capacitor is variable; its capacitance can be adjusted to set the crossover point according to the frequency response of the woofer and tweeter. What should the capacitance be set t
> Suppose a uniform electric field of magnitude 100.0 N/C exists in a region of space. How far apart are a pair of equipotential surfaces whose potentials differ by 1.0 V?
> On a graph of x versus time, what quantity does the slope of the graph represent?
> A cosmic-ray proton entering the atmosphere from space has a kinetic energy of 2.0 × 1020 eV. (a) What is its kinetic energy in joules? (b) If all of the kinetic energy of the proton could be harnessed to lift an object of mass 1.0 kg near Earth's surfa
> What is the angular acceleration of the dipole at θ = 135°?
> A whimsical statement of the laws of thermodynamics—probably not one favored by gamblers—goes like this: I. You can never win; you can only lose or break even. II. You can only break even at absolute zero. III. You can never get to absolute zero. What do
> A seismic wave is described by the equation The wave travels through a uniform medium along the x-axis. (a) Is this wave moving right (+x-direction) or left (−x-direction)? (b) How far from their equilibrium positions do the particles
> The first nuclear reaction ever observed (in 1919 by Ernest Rutherford) was / . (a) Identify the reaction product “(?).” (b) For this reaction to take place, the alpha particle must come in contact with the nitrogen nucleus. Calculate the distance d bet
