Question: Some digital thermometers measure the current

> Why must a camera or a projector use a converging lens? Why must the objective of a microscope or telescope be a converging lens (or a converging mirror)? Why can the eyepiece of a telescope be either converging or diverging?

> When you eat a pizza that has just come from the oven, why is it that you are apt to burn the roof of your mouth with the first bite although the crust of the pizza feels only warm to your hand?

> Rank the final speeds of the three rocks.

> 4A strip of copper 2.0 cm wide carries a current I = 30.0 A to the right. The strip is in a magnetic field B = 5.0 T into the page. (a) What is the direction of the average magnetic force on the conduction electrons? (b) The Hall voltage is 20.0 μV. Wha

> (a) Find the value of a single capacitor to replace the three capacitors in the diagram. (b) What is the potential difference across the 12 µF capacitor at the left side of the diagram? (c) What is the charge on the 12 µF capa

> Find the magnetic field at point P, the midpoint of the top side of the square.

> An external magnetic field parallel to the central axis of a 50 turn coil of radius 5.0 cm increases from 0 to 1.8 T in 3.6 s. (a) If the resistance of the coil is 2.8 Ω, what is the magnitude of the induced current in the coil? (b) What is the directi

> A sound wave with an intensity level of 80.0 dB is incident on an eardrum of area 0.600 × 10−4 m2. How much energy is incident on the eardrum in 3.00 min?

> Describe the difference between specular and diffuse reflection. Give some examples of each.

> The mechanical power output of a cyclist moving at a constant speed of 6.0 m/s on a level road is 120 W. (a) What is the force exerted on the cyclist and the bicycle by the air? (b) By bending low over the handlebars, the cyclist reduces the air resist

> When the NASA Rover Spirit successfully landed on Mars in January of 2004, Mars was 170.2 × 106 km from Earth. Twenty-one days later, when the Rover Opportunity landed on Mars, Mars was 198.7 × 106 km from Earth. (a) How long did it take for a one-way t

> The period of oscillation of a simple pendulum does not depend on the mass of the bob. By contrast, the period of a mass-spring system does depend on mass. Explain the apparent contradiction. [Hint: What provides the restoring force in each case? How doe

> Is the buoyant force on a soap bubble greater than the weight of the bubble? If not, why do soap bubbles sometimes appear to float in air?

> Show that each of these statements implies that v ≪ c, which means that v can be considered a nonrelativistic speed: (a) γ − 1 ≪ 1 [Eq. (26-26)]; (b) K ≪ mc2 [Eq. (26-27)]; (c) p ≪ mc [Eq. (26-28)]; (d) K ≈ p2/(2m).

> An automobile with a mass of 1600 kg has a speed of 30.0 m/s. What is its kinetic energy?

> 1. The compound microscope is made from two lenses. Which statement is true concerning the operation of the compound microscope? (a) Both lenses form real images. (b) Both lenses form virtual images. (c) The lens closest to the object forms a virtual ima

> 1. A baryon can be composed of (a) any odd number of quarks. (b) three quarks with three different colors. (c) three quarks of matching color. (d) a colorless quark-antiquark pair. 2. Mesons are composed of (a) any odd number of quarks. (b) three quarks

> In Problem 13, what is the kinetic energy of the muon? [Hint: The muon is nonrelativistic, so its kinetic energy-momentum relationship is K = p2/(2m). The antineutrino is extremely relativistic.]

> Give an example of an object whose acceleration is (a) in the same direction as its velocity, (b) opposite its velocity, and (c) perpendicular to its velocity.

> 1. Solid lead has more than four times the mass density of solid aluminum. What is the main reason that lead is so much more dense? (a) The Pb atom is smaller than the Al atom. (b) The Pb nucleus is smaller than the Al nucleus. (c) The Pb nucleus is more

> An ac circuit contains a 12.5 Ω resistor, a 5.00 µF capacitor, and a 3.60 mH inductor connected in series to an ac generator with an output voltage of 50.0 V (peak) and frequency of 1.59 kHz. Find the impedance, the power factor, and the phase difference

> Suppose a satellite is in a circular orbit 3.0 Earth radii above the surface of Earth (4.0 Earth radii from the center of Earth). By how much does it have to increase its speed in order to be able to escape Earth? [Hint: You need to calculate the orbital

> A harpsichord string is made of yellow brass (Young's modulus 90 GPa, tensile strength 0.63 GPa, mass density 8500 kg/m3). When tuned correctly, the tension in the string is 59.4 N, which is 93% of the maximum tension that the string can endure without b

> When batteries are connected in parallel, they should have the same emf. However, batteries connected in series need not have the same emf. Explain.

> Four objects move to the right with constant acceleration. Rank the motion diagrams in order of the magnitude of the acceleration, from greatest to least. The time interval between dots is the same in each diagram.

> Some claim that mountain climbers suffer from headaches due not only to a lack of oxygen in the brain, but also to the expansion of the brain in the cranium. Find the fractional change of the brain’s volume due to a reduction in pressure from 101 kPa at

> In the study of thermodynamics, we thought of a refrigerator as a reversed heat engine. (a) Explain how a generator is a reversed electric motor. (b) What kind of device is a reversed loudspeaker?

> One of the tricky things about learning to sail is distinguishing the “true wind” from the “apparent wind.” The true wind is the velocity of the air relative to the water, whereas th

> A person is doing leg lifts with 3.0 kg ankle weights. She is sitting in a chair with her legs bent at a right angle initially. The quadriceps muscles are attached to the patella via a tendon; the patella is connected to the tibia by the patellar tendon,

> A framed poster is covered with glass that has a rougher surface than regular glass. How does a rough surface reduce glare?

> In fair weather, over flat ground, there is a downward electric field of about 150 NlC. Assume that Earth is a conducting sphere with charge on its surface. If the electric field just outside is 150 N/C pointing radially inward, calculate the total charg

> Some bats determine their distance to an object by detecting the difference in intensity between echoes. (a) If intensity falls off at a rate that is inversely proportional to the distance squared, show that the echo intensity is inversely proportional

> For high-frequency sounds, the ear's principal method of localization is the difference in intensity sensed by the two ears. Why can't the ear reliably use this method for low-frequency sounds? Doesn't the head cast a “sound shadow” regardless of the fre

> What is the relationship between average velocity and instantaneous velocity? An object can have different instantaneous velocities at different times. Can the same object have different average velocities? Explain.

> 1. Two particles A and B of equal mass are located at some distance from each other. Particle A is at rest while B moves away from A at speed v. What happens to the center of mass of the system of two particles? (a) It does not move. (b) It moves with a

> 1. After getting on the Santa Monica Freeway, a sports car accelerates from 30 mi/h to 90 mi/h. Its kinetic energy (a) increases by a factor of /. (b) increases by a factor of 3. (c) increases by a factor of 9. (d) increases by a factor that depends on

> If diffraction were the only limitation on resolution, what would be the smallest structure that could be resolved in an electron microscope using 10 keV electrons?

> Unpolarized light is incident on four ideal polarizing sheets with their transmission axes oriented as shown in the figure. What percentage of the initial light intensity is transmitted through this set of polarizers?

> A raindrop inside a thundercloud has charge −8e. What is the electric force on the raindrop if the electric field at its location (due to other charges in the cloud) has magnitude 2.0 × 106 N/C and is directed upward?

> An alpha particle (helium nucleus, charge +2e) starts from rest and travels a distance of 1.0 cm under the influence of a uniform electric field of magnitude 10.0 kV/m. What is the final kinetic energy of the alpha particle?

> Refer to Fig. 20.2. The rod has length L and its position is x at some instant, as shown in the figure. Express your answers in terms of x, L, v, B (the magnetic field magnitude), and R, as needed. (a) What is the area enclosed by the conducting loop at

> An air ionizer filters particles of dust, pollen, and other allergens from the air using electric forces. In one type of ionizer (see diagram), a stream of air is drawn in with a speed of 3.0 m/s. The air passes through a fine, highly charged wire mesh t

> Two identical pucks are on an air table. Puck A has an initial velocity of 2.0 m/s in the +x-direction. Puck B is at rest. Puck A collides with puck B, and A moves off at 1.0 m/s at an angle of 60° above the x- axis. (a) What are the speed and direction

> It takes longer to hard-boil an egg in Mexico City (2200 m above sea level) than it does in Amsterdam (parts of which are below sea level). Why? [Hint: At higher altitudes, water boils at less than 100°C.]

> Rank the flywheels in order of angular speed, largest to smallest. Explain.

> Photons with a wavelength of 400 nm are incident on an unknown metal, and electrons are ejected from the metal. However, when photons with a wavelength of 700 nm are incident on the metal, no electrons are ejected. (a) Could this metal be cesium with a

> A 0.50 m long guitar string, of cross-sectional area 1.0 × 10−6 m2, has Young’s modulus Y = 2.0 GPa. By how much must you stretch the string to obtain a tension of 20 N?

> At what frequency/does a sound wave in air have a wavelength of 15 cm, about half the diameter of the human head? Some methods of localization work well only for frequencies below f, whereas others work well only above f. (See Conceptual Questions 4 and

> The distance between atoms in a crystal of NaCl is 0.28 nm. The crystal is being studied in a neutron diffraction experiment. At what speed must the neutrons be moving so that their de Broglie wavelength is 0.28 nm?

> An array of four charges is arranged along the x-axis at intervals of 1.0 m. (a) If two of the charges are +1.0 µC and two are −1.0 µC, draw a configuration of these charges that minimizes the potential at x =

> Why is the brilliance of an artificial diamond made of cubic zirconia (n = 1.9) distinctly inferior to the real thing (n = 2.4) even if the two are cut the same way? How would an artificial diamond made of glass compare?

> A 15 A circuit breaker trips repeatedly. Explain why it would be dangerous to replace it with a 20 A circuit breaker.

> A 0.010 kg bullet traveling horizontally at 400.0 m/s strikes a 4.0 kg block of wood sitting at the edge of a table. The bullet is lodged into the wood. If the table height is 1.2 m, how far from the table does the block hit the floor?

> This problem illustrates the ideas behind the Millikan oil drop experiment—the first measurement of the electron charge. Millikan examined a fine spray of spherical oil droplets falling through air; the drops had picked up an electric charge as they were

> In each of six situations, a particle (mass m, charge q) is located at a point where the electric field has magnitude E. No other forces act on the particles. Rank them in order of the magnitude of the particle’s acceleration, from largest to smallest. (

> Ultraviolet light of wavelength 220 nm illuminates a tungsten surface, and electrons are ejected. A stopping potential of 1.1 V is able to just prevent any of the ejected electrons from reaching the opposite electrode. What is the work function for tungs

> Suppose d = 3.25λ. (a) In terms of λ, what is the difference in the path lengths traveled by the waves that arrive at the detector at θ = 0? (b) What is the difference in the path lengths traveled by the waves tha

> The flux through a closed surface is zero. Is the electric field necessarily zero? Is the net charge inside the surface necessarily zero? Explain your answers.

> The FM radio band is broadcast between 88 MHz and 108 MHz. What range of capacitors must be used to tune in these signals if an inductor of 3.00 µH is used?

> One day when your friend from Problem 43 is picking up a package, you notice that he bends at the waist to pick it up rather than keeping his back straight and bending his knees. You suspect that the lower back pain he complains about is caused by the la

> Charges of +2.0 nC and −1.0 nC are located at opposite corners, A and C, respectively, of a square which is 1.0 m on a side. What is the electric potential at a third corner, B, of the square (where there is no charge)?

> Rank these nuclides in decreasing order of the number of neutrons: (a) (b) (c) (d) (e) (f)

> (a) A proton moves with uniform circular motion in a magnetic field of magnitude 0.80 T. At what frequency f does it circulate? (b) Repeat for an electron.

> The orbital speed of Earth about the Sun is 3.0 × 104 m/s and its distance from the Sun is 1.5 × 1011 m. The mass of Earth is approximately 6.0 × 1024 kg and that of the Sun is 2.0 × 1030 kg. What is the magnitude of the force exerted by the Sun on Earth

> The average adult has about 5 L of blood, and a healthy adult heart pumps blood at a rate of about 80 cm3/s. Estimate how long it takes for medicine delivered intravenously to travel throughout a person’s body.

> Muons are created by cosmic-ray collisions at an elevation h (as measured in Earth's frame of reference) above Earth's surface and travel downward with a constant speed of 0.990c. During any time interval of 1.5 µs in the rest frame of the muons, half of

> As an electron moves through a region of space, its speed decreases from 8.50 × 106 m/s to 2.50 × 106 m/s. The electric force is the only force acting on the electron. (a) Did the electron move to a higher potential or a lower potential? (b) Across what

> A ray reflects from a spherical mirror at point P. Explain why a radial line from the center of curvature through point P always bisects the angle between the incident and reflected rays.

> Refer to Problem 40. You chose an angle θ of 33.8°. An 8.7 kg raccoon has climbed onto the beam and is walking from the wall toward the point where the cable meets the beam. How far can the raccoon walk before the cable breaks?

> The word flux comes from the Latin “to flow.” What does the quantity ΦE = E⊥ A have to do with flow? The figure shows some streamlines for the flow of water in a pipe. The streamlines are

> Refer to Atwood's machine (Example 8.2). (a) Assuming that the cord does not slip as it passes around the pulley, what is the relationship between the angular acceleration of the pulley (α) and the magnitude of the linear acceleration of the blocks (a)?

> Until the Supreme Court ruled it to be unconstitutional, drug enforcement officers examined buildings at night with a camera sensitive to infrared. How did this help them identify marijuana growers?

> What determines the direction of heat flow when two objects at different temperatures are placed in thermal contact?

> Think of a wire of cross-sectional area A as two wires of area A/2 in parallel. Construct an argument for why the resistance of a wire must be inversely proportional to its cross-sectional area.

> An airplane starts from rest on the runway. The engines exert a constant force of 78 kN on the body of the plane (mass 9.2 × 104 kg) during takeoff. How far down the runway does the plane reach its takeoff speed of 68 m/s?

> Sean climbs a tower that is 82.3 m high to make a jump with a parachute. The mass of Sean plus the parachute is 68.0 kg. If U = 0 at ground level, what is the potential energy of Sean and the parachute at the top of the tower?

> A bar magnet approaches a coil as shown. (a) In which direction does current flow through the galvanometer as the magnet approaches? (b) How does the magnitude of the current depend on the number of turns in the coil? (The resistance of the coil is neg

> A 69.0 kg short-track ice skater is racing at a speed of 11.0 m/s when he falls down and slides across the ice into a padded wall that brings him to rest. Assuming that he doesn’t lose any speed during the fall or while sliding across the ice, how much w

> The human mandible (lower jaw) is attached to the temporomandibular joint (TMJ). The masseter muscle is largely responsible for pulling the mandible upward when you are talking or eating. It is attached at a horizontal distance of about 2.5 cm from the T

> A bar magnet is initially at rest inside a coil as shown. The magnet is then pulled out from the left side. (a) In which direction does current flow through the galvanometer as the magnet is pulled away? (b) How would the magnitude of the current chang

> If the potential is the same at every point throughout a region of space, is the electric field the same at every point in that region? What can you say about the magnitude of / in the region? Explain.

> Two ions with the same velocity and mass but different charges enter the magnetic field of a mass spectrometer. One is singly charged (q = +e) and the other is doubly charged (q = +2e). Is the radius of their circular paths the same? If not, which is lar

> Find the average angular speed of the second hand of an analog clock. What is its angular displacement during 5.0 s?

> When a standing wave is produced in a string fixed at both ends, the string oscillates so fast that it looks like a blur. You want to photograph the string when it is at positions A, B, and C shown in the figure. The tension in the string is 2.00 N and i

> A parallel-plate capacitor consists of two flat metal plates of area A separated by a small distance d. The plates are given equal and opposite net charges ±q. (a) Sketch the field lines and use your sketch to explain why almost all of the charge is on

> A 200 W infrared laser emits photons with a wavelength of 2.0 × 10−6 m, and a 200 W ultraviolet light emits photons with a wavelength of 7.0 × 10−8 m. (a) Which has greater energy, a single infrared photon or a single ultraviolet photon? (b) What is th

> A negatively charged rod is brought near a grounded conductor. After the ground connection is broken, the rod is removed. Is the charge on the conductor positive, negative, or zero? Explain.

> Bacteria swim using a corkscrew-like helical flagellum that rotates. For a bacterium with a flagellum that has a pitch of 1.0 μm that rotates at 110 rev/s, how fast could it swim if there were no “slippage” in the medium in which it is swimming? The pitc

> Draw a diagram of the human eye, labeling the cornea, the lens, the iris, the retina, and the aqueous and vitreous fluids.

> A positive charge +2 µC and a negative charge −5 µC lie on a line. In which region or regions (A, B, C) is there a point on the line a finite distance away where the potential is zero? Explain your reasoning. A

> A negatively charged particle with charge −q is far away from a positive charge +Q that is fixed in place. As −q moves closer to +Q, (a) does the electric field do positive or negative work? (b) Does −q move through a potential increase or a potential d

> A thin aluminum target is illuminated with photons of wavelength λ. A detector is placed at 90.0° to the direction of the incident photons. The scattered photons detected are found to have half the energy of the incident photons. (a) Find λ. (b) What i

> The following hypothetical reaction shows a neutron (n) decaying into a proton (p+), an electron (e−), and an uncharged particle called an antineutrino/ : At first there is no charge, but then charge seems to be “crea

> It is commonly said that wood floats because it is “lighter than water” or that a stone sinks because it is “heavier than water.” Are these accurate statements? If not, correct them.

> Young’s modulus for diamond is about 20 times as large as that of glass. Does that tell you which is stronger? If not, what does it tell you?

> (a) How much energy is stored in the inductor at t = 0? (b) What is the instantaneous rate of change of the inductor’s energy at t = 0? (c) What is the average rate of change of the inductor’s energy between t = 0.0 and t = 1.0 s?

> The pilot of a small plane finds that the airport where he intended to land is fogged in. He flies 55 mi west to another airport to find that conditions there are too icy for him to land. He flies 25 mi at 15° east of south and is finally able to land at

> Photoelectric experiments are performed with five different metals. Given the work function of the metal ϕ and the energy of the incident photons E, rank the experiments in order of the stopping potential, largest to smallest. (a) ϕ = 2.0 eV, E = 2.8 eV

> A chain pulls tangentially on a 40.6 kg uniform cylindrical gear with a tension of 72.5 N. The chain is attached along the outside radius of the gear at 0.650 m from the axis of rotation. Starting from rest, the gear takes 1.70 s to reach its rotational

> An object of mass 3.0 kg is allowed to fall from rest under the force of gravity for 3.4 s. What is the change in its momentum? Ignore air resistance.