Question: When a proton and an antiproton annihilate,

> 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.

> A small plane is flying directly west with an airspeed of 30.0 m/s. The plane flies into a region where the wind is blowing at 10.0 m/s at an angle of 30° to the south of west. In that region, the pilot changes her heading to maintain her course due west

> Suppose that a horizontal electron beam is deflected to the right by a uniform magnetic field. What is the direction of the magnetic field? If there is more than one possibility, what can you say about the direction of the field?

> In her bathroom, Mindy has an overhead heater that consists of a coiled wire made of nichrome that gets hot when turned on. The wire has a length of 3.0 m when it is uncoiled. The heating element is attached to the normal 120 V wiring, and when the wire

> A lightweight plastic rod is rubbed with a piece of fur. A second plastic rod, hanging from a string, is attracted to the first rod and swings toward it. When the second rod touches the first, it is suddenly repelled and swings away. Explain what has hap

> Your laboratory partner hands you a glass rod and asks if it has negative charge on it. There is an electroscope in the laboratory. How can you tell if the rod is charged? Can you determine the sign of the charge? If the rod is charged to begin with, wil

> Many real estate agents have an ultrasonic rangefinder that enables them to quickly and easily measure the dimensions of a room. The device is held to one wall and reads the distance to the opposite wall. How does it work?

> A spring scale in a French market is calibrated to show the mass of vegetables in grams and kilograms. (a) If the marks on the scale are 1.0 mm apart for every 25 g, what maximum extension of the spring is required to measure up to 5.0 kg? (b) What is

> Suppose that a string of length L and mass m is under tension F. (a) Show that has units of speed. (b) Show that there is no other combination of L, m, and F with units of speed. [Hint: Of the dimensions of the three quantities L, m, and F, only F in

> Crocodiles are thought to be able to detect changes in the flux due to Earth’s magnetic field as they move their heads. Suppose a crocodile is initially facing north. The horizontal component of Earth’s magnetic field is 30 μT. Consider a vertical, circu

> Suppose that as you travel away from Earth in a spaceship, you observe another ship pass you heading in the same direction and measure its speed to be 0.50c. As you look back at Earth, you measure Earth's speed relative to you to be 0.90c. What is the sp

> A rod is negatively charged by rubbing it with fur. It is brought near another rod of unknown composition and charge. There is a repulsive force on each. (a) Is the first rod an insulator or a conductor? Explain. (b) What can you tell about the charge o

> An object has a mass of 12.6 kg and a speed of 0.87c. (a) What is the magnitude of its momentum? (b) If a constant force of 424.6 N acts in the direction opposite to the object's motion, how long must the force act to bring the object to rest? [Hint: U

> The time to sunset can be estimated by holding out your arm with your fingers perpendicular to the path the Sun will follow to the horizon. The number of fingers that fit between the Sun and the sunset point is proportional to the time remaining. (a) Wh

> A concave mirror has focal length f. (a) If you look into the mirror from a distance less than f, is the image you see upright or inverted? (b) If you stand at a distance greater than 2f, is the image upright or inverted? (c) If you stand at a distance

> What happens if a 40 W incandescent lightbulb, designed to be connected to an ac voltage with amplitude 170 V and frequency 60 Hz, is instead connected to a 170 V dc power supply? Explain. What dc voltage would make the lightbulb burn with the same brigh

> A hedge trimmer has a blade that moves back and forth with a frequency of 28 Hz. The blade motion is converted from the rotation of an electric motor to oscillatory motion by means of a Scotch yoke (see Conceptual Question 7). The blade moves 2.4 cm from

> Why does the resistivity of a metallic conductor increase with increasing temperature?

> Electronic devices are usually enclosed in metal boxes. One function of the box is to shield the inside components from external electric fields. (a) How does this shielding work? (b) Why is the degree of shielding better for constant or slowly varying

> A particle decays in flight into two pions, each having a rest energy of 140.0 MeV. The pions travel at right angles to each other with equal speeds of 0.900c. Find (a) the momentum magnitude of the original particle, (b) its kinetic energy, and (c) i

> A roller coaster car of mass 320 kg (including passengers) travels around a horizontal curve of radius 35 m. Its speed is 16 m/s. (a) What are the magnitude and direction of the total force exerted on the car by the track? (b) What is the banking angle

> In this problem, use Ampere's law to show that the magnetic field inside a long solenoid is B = μ0nI. Assume that the field inside the solenoid is uniform and parallel to the axis and that the field outside is zero. Choose a rectangular pat

> A 2.0 kg object is at rest on a frictionless surface when it is hit by a 3.0 kg object moving at 8.0 m/s. If the two objects are stuck together after the collision, what is the speed of the combination?

> A mass-and-spring system oscillates with amplitude A and angular frequency ω. (a) What is the average speed during one complete cycle of oscillation? (b) What is the maximum speed? (c) Find the ratio of the average speed to the maximum speed. (d) Ske

> A metal sphere is initially uncharged. After being touched by a charged rod, the metal sphere is positively charged. (a) Is the mass of the sphere larger, smaller, or the same as before it was charged? Explain. (b) What sign of charge is on the rod?

> A road with a radius of 75.0 m is banked so that a car can navigate the curve at a speed of 15.0 m/s without any friction. On a cold day when the street is icy, the coefficient of static friction between the tires and the road is 0.120. What is the slowe

> A horizontal spring with spring constant of 9.82 N/m is attached to a block with a mass of 1.24 kg that sits on a frictionless surface. When the block is 0.345 m from its equilibrium position, it has a speed of 0.543 m/s. (a) What is the maximum displac

> Both a microscope and a telescope can be constructed from two converging lenses. What are the differences? Why can't a telescope be used as a microscope? Why can't a microscope be used as a telescope?

> A battery has a terminal voltage of 12.0 V when no current flows. Its internal resistance is 2.0 Ω. If a 1.0 Ω resistor is connected across the battery terminals, what is the terminal voltage and what is the current through the 1.0 Ω resistor?

> A high-speed dental drill is rotating at 3.14 × 104 rad/s. Through how many degrees does the drill rotate in 1.00 s?

> Can an astronaut on the Moon use a straw to drink from a normal drinking glass? How about if he pokes a straw through an otherwise sealed juice box? Explain.

> Explain how it is possible that more than half of the molecules in an ideal gas have kinetic energies less than the average kinetic energy. Shouldn't half have less and half have more?

> The sound level 25 m from a loudspeaker is 71 dB. What is the rate at which sound energy is produced by the loudspeaker, assuming it to be an isotropic source?

> A straight, stiff wire of length 1.00 m and mass 25 g is suspended in a magnetic field B = 0.75 T. The wire is connected to an emf. How much current must flow in the wire and in what direction so that the wire is suspended and the tension in the supporti

> A sound wave in room-temperature air has an intensity level of 65.0 dB and a frequency of 131 Hz. (a) What is the pressure amplitude? (b) What is the displacement amplitude?

> A bicycle and its rider together have a mass of 75 kg. What power output of the rider is required to maintain a constant speed of 4.0 m/s (about 9 mi/h) up a 5.0% grade (a road that rises 5.0 m for every 100 m along the pavement)? Assume that frictional

> In the figure, switch S is initially open. It is closed, and then opened again a few seconds later. (a) In what direction does current flow through the ammeter when switch S is closed? (b) In what direction does current flow when switch S is then opene

> What is the mass of one gold atom in kilograms?

> A circuit has a resistor and an unknown component in series with a 12 V (rms) sinusoidal ac source. The current in the circuit decreases by 20% when the frequency decreases from 240 Hz to 160 Hz. What is the second component in the circuit? Explain your

> Two speakers spaced a distance 1.5 m apart emit coherent sound waves at a frequency of 680 Hz in all directions. The waves start out in phase with each other. A listener walks in a circle of radius greater than 1 m centered on the midpoint of the two spe

> 1. An electron, passing close to a target nucleus, slows and radiates away some of its energy. What is this process called? (a) Compton effect (b) photoelectric effect (c) bremsstrahlung (d) blackbody radiation (e) stimulated emission 2. How many emissi

> A pendulum is made from a uniform rod of mass m1 and a small block of mass m2 attached at the lower end. (a) If the length of the pendulum is L and the oscillations are small, find the period of the oscillations in terms of m1, m2, L, and g. (b) Check

> Explain why electric field lines begin on positive charges and end on negative charges. [Hint: What is the direction of the electric field near positive and negative charges?]

> A biologist is studying plant growth and wants to simulate a gravitational field twice as strong as Earth’s. She places the plants on a horizontal rotating table in her laboratory on Earth at a distance of 12.5 cm from the axis of rotat

> Explain why any net charge on a solid metal conductor in electrostatic equilibrium is found on the outside surface of the conductor instead of being distributed uniformly throughout the solid.

> What makes clothes cling together—or to your body—after they’ve been through the dryer? Why do they not cling as much if they are taken out of the dryer while slightly damp? In which case would you expect your clothes to cling more, all other things bein

> A wooden barrel full of water has a flat circular top of radius 25.0 cm with a small hole in it. A tube of height 8.00 m and inner radius 0.250 cm is suspended above the barrel with its lower end inserted snugly in the hole. Water is poured into the uppe

> Two children are playing with a tin-can telephone. The children are 12 m apart, the string connecting their tin cans has a linear mass density of 1.3 g/m, and it is stretched with a tension of 8.0 N. One child decides to pluck the string. How long does i

> A proposed “space elevator” consists of a cable going all the way from the ground to a space station in geostationary orbit (always above the same point on Earth’s surface). Elevator “cars” would climb the cable to transport cargo to outer space. Conside

> A convex mirror produces an image located 18.4 cm behind the mirror when an object is placed 32.0 cm in front of the mirror. What is the focal length of this mirror?

> At t = 0, six birds are flying south at 10 m/s. Their masses and their velocities at a later time are: (a) 200 g, 10 m/s north at t = 30 s (b) 200 g, 10 m/s east at t = 30 s (c) 200 g, 20 m/s north at t = 60 s (d) 400 g, 20 m/s north at t = 60 s (e) 400

> A cup of hot coffee has been poured, but the coffee drinker has a little more work to do at the computer before she picks up the cup. She intends to add some milk to the coffee. To keep the coffee hot as long as possible, should she add the milk at once,

> In a circus trapeze act, two acrobats fly through the air and grab on to each other, then together grab a swinging bar. One acrobat, with a mass of 60 kg, is moving at 3.0 m/s at an angle of 10° above the horizontal, and the other, with a mass of 80 kg,

> Two factors that can determine the distance over which a force can act are the mass of the exchange particle that carries the force and the Heisenberg uncertainty principle [Eq. (28-5)]. Assume that the uncertainty in the energy of an exchange particle i

> When the temperature as measured in °C of a radiating object is doubled (such as a change from 20°C to 40°C), is the radiation rate necessarily increased by a factor of 16?

> A 5.0 mH inductor and a 10.0 Q resistor are connected in series with a 6.0 V dc battery. (a) What is the voltage across the resistor immediately after the switch is closed? (b) What is the voltage across the resistor after the switch has been closed fo

> At very low temperatures, the molar specific heat of hydrogen (H2) is CV = 1.5R. At room temperature, CV = 2.5R. Explain.

> Calculate the value of (a) Planck's constant and (b) the work function of the metal from the data obtained by Robert A. Millikan in 1916, as shown in the graph. Millikan was attempting to disprove Einstein's photoelectric equation; instead he found tha

> Explain why two waves of significantly different frequencies cannot be coherent.

> Medical testing has established that the maximum acceleration a pilot can be subjected to without losing consciousness is approximately 5.0g if the axis of acceleration is aligned with the spine. (See Example 5.4.) A pilot can avoid “blackout” at acceler

> Why can a neutron within a nucleus be stable, whereas an isolated neutron is unstable? What determines whether a neutron within a nucleus is stable? [Hint: Consider conservation of energy.]

> At what time is the current in the inductor 0.0010 times its initial value?

> A spy satellite is in circular orbit around Earth. It makes one revolution in 6.00 h. (a) How high above Earth’s surface is the satellite? (b) What is the satellite’s acceleration?

> A velodrome is built for use in the Olympics. The radius of curvature of the surface is 20.0 m. At what angle should the surface be banked for cyclists moving at 18 m/s? (Choose an angle so that no frictional force is needed to keep the cyclists in their

> A square loop of wire, 0.75 m on each side, has one edge along the positive z-axis and is tilted toward the yz-plane at an angle of 30.0° with respect to the horizontal (xz-plane). There is a uniform magnetic field of 0.32 T pointing in the po

> Explain why the molar specific heat of a diatomic gas such as O2 is larger than that of a monatomic gas such as Ne.

> A room air conditioner causes a temperature change of −6.0°C. (a) What is the temperature change in kelvins? (b) What is the temperature change in °F?

> Repeat Problem 37 for an operating frequency of 98.7 Hz. (a) What is the phase angle for this circuit? (b) Draw the phasor diagram. (c) What is the resonant frequency for this circuit?

> Approximately what is the total energy of the neutrino emitted when / decays by electron capture?

> While an elevator of mass 2530 kg moves upward, the tension in the cable is 33.6 kN. (a) What is the acceleration of the elevator? (b) If at some point in the motion the velocity of the elevator is 1.20 m/s upward, what is the elevator’s velocity 4.00 s