A 10.0 kg block is released from rest on a frictionless track inclined at an angle of 55°. (a) What is the net force on the block after it is released? (b) What is the acceleration of the block? (c) If the block is released from rest, how long will it take for the block to attain a speed of 10.0 m/s? (d) Draw a motion diagram for the block. (e) Draw a graph of vx(t) for values of velocity between 0 and 10 m/s. Let the positive x-axis point down the track.
> 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
> An electric mixer is being used to mix up some cake batter. What happens to the motor if the batter is too thick, so the beaters are turning slowly?
> In Section 25.3 we studied interference due to thin films. Why must the film be thin? Why don't we see interference effects when looking through a window or at a poster covered by a plate of glass—even if the glass is optically flat?
> Can sound waves be polarized? Explain.
> An electron (charge −e) is projected horizontally into the space between two oppositely charged parallel plates. The electric field between the plates is 500.0 N/C upward. If the vertical deflection of the electron as it leaves the plates has magnitude 3
> Think of a wire of length L as two wires of length L/2 in series. Construct an argument for why the resistance of a wire must be proportional to its length.
> A battery is connected to a clock by copper wires as shown. What is the direction of current through the clock (B to C or C to B)? What is the direction of current through the battery (D to A or A to D)? Which terminal of the battery is at the higher pot
> Some batteries can be “recharged.” Does that mean that the battery has a supply of charge that is depleted as the battery is used? If “recharging” does not literally mean to put char
> To resolve details of a cell using an ordinary microscope, you must use a wavelength that is about the same size, or smaller, than the details of the cell you want to observe. Suppose you want to be able to see the ribosomes, which are about 20 nm in dia
> In this problem, you will estimate the smallest kinetic energy of vibration that the human ear can detect. Suppose that a harmonic sound wave at the threshold of hearing (I = 1.0 × 10−12 W/m2) is incident on the eardrum. Take the speed of sound as 340 m/
> 11. An object is in nonuniform circular motion with constant angular acceleration. Identify the correct statement(s). (Use the same answer choices as in Question 10.) (a) 1 only (b) 2 only (c) 3 only (d) 1, 2, and 3 (e) 2 and 3 (f) 1 and 2 (g) 1 and 3 (h
> A motorist driving a 1200 kg car on level ground accelerates from 20.0 m/s to 30.0 m/s in a time of 5.0 s. Ignoring friction and air resistance, determine the average mechanical power in watts the engine must supply during this time interval.
> A parallel plate capacitor has a charge of 0.020 µC on each plate with a potential difference of 240 V. The parallel plates are separated by 0.40 mm of air. (a) What is the capacitance for this capacitor? (b) What is the area of a single plate? (c) At
> When the viola section of an orchestra with six members plays together, is the sound 6 times as loud as when a single viola plays? Explain. Is the intensity 6 times what it would be for a single viola? [Hint: The six sound waves are not coherent.]
> Why don't you see an interference pattern on your desk when you have light from two different lamps illuminating the surface?
> Derivation of the Doppler formula for light. A source and observer of EM waves move relative to each other at velocity v. Let v be positive if the observer and source are moving apart from each other. The source emits an EM wave at frequency fs (measured
> A pion (mass 0.140 GeV/c2) at rest decays by the weak interaction into a muon of mass 0.106 GeV/c2 and a muon antineutrino: What is the total kinetic energy of the muon and the antineutrino?
> A spring of negligible mass is compressed between two blocks, A and B, which are at rest on a frictionless horizontal surface at a distance of 1.0 m from a wall on the left and 3.0 m from a wall on the right. The sizes of the blocks and spring are small.
> A variable capacitor is made of two parallel semicircular plates with air between them. One plate is fixed in place and the other can be rotated. The electric field is zero everywhere except in the region where the plates overlap. When the plates are dir
> What is the average linear speed of Earth about the Sun?
> A 1500 kg car coasts in neutral down a 2.0° hill. The car attains a terminal speed of 20.0 m/s. (a) How much power must the engine deliver to drive the car on a level road at 20.0 m/s? (b) If the maximum useful power that can be delivered by the engine
> The figure shows standing wave patterns in five pipes of equal length. Pipes (c) and (e) are open at both ends; the others are closed at one end. Rank the standing waves in order of the frequency, largest to smallest.
> Rhonda keeps a 2.0 kg model airplane moving at constant speed in a horizontal circle at the end of a string of length 1.0 m. The tension in the string is 18 N. How much work does the string do on the plane during each revolution?
> A charged pion can decay either into a muon or an electron. The two decay modes of a π− are: / And / . Write the two decay modes for the π+. [Hint: π+ is the antiparticle of π−. Replace each particle in the decay reaction with its corresponding antipa
> A coil of wire is connected to an ideal 6.00 V battery at t = 0. At t = 10.0 ms, the current in the coil is 204 mA. One minute later, the current is 273 mA. Find the resistance and inductance of the coil. [Hint: Sketch I(t).]
> A police car’s radar gun emits microwaves with a frequency of f1 = 36.0 GHz. The beam reflects from a speeding car, which is moving away at 43.0 m/s with respect to the police car. The frequency of the reflected microwave as observed by the police is f2.
> A bicycle wheel, of radius 0.30 m and mass 2 kg (concentrated on the rim), is rotating at 4.00 rev/s. After 50 s the wheel comes to a stop because of friction. What is the magnitude of the average torque due to frictional forces?
> A spherical balloon with a radius of 12.0 cm is filled with helium. The bottom of the balloon is attached to a 2.30 m length of ribbon that is anchored to the ground. The balloon alone has a mass of 2.80 × 10−3 kg. Ignore the mass of the ribbon. (a) Wha
> The figure shows a magnetic dipole antenna transmitting an electromagnetic wave. At a point P far from the antenna, what are the directions of the electric and magnetic fields of the wave?
> A bird perched on a power line is not harmed, but if you are pruning a tree and your metal pole saw comes in contact with the same wire, you risk being electrocuted. Explain.
> A negatively charged particle of mass 5.00 × 10−19 kg is moving with a speed of 35.0 m/s when it enters the region between two parallel capacitor plates. The initial velocity of the charge is parallel to the plate surfaces
> When a coin is tossed directly upward, what can you say about its velocity and acceleration at the high point of the toss?
> A container is filled with gas at a pressure of 4.0 × 105 Pa. The container is a cube, 0.10 m on a side, with one side facing south. What is the magnitude and direction of the force on the south side of the container due to the gas inside?
> A fisherman notices a buoy bobbing up and down in the water in ripples produced by waves from a passing speedboat. These waves travel at 2.5 m/s and have a wavelength of 7.5 m. At what frequency does the buoy bob up and down?
> An RLC circuit has a resistance of 10.0 Ω, an inductance of 15.0 mH, and a capacitance of 350 µF. By what factor does the impedance of this circuit change when the frequency at which it is driven changes from 60 Hz to 120 Hz? Does the impedance increase
> An electrician working on “live” circuits wears insulated shoes and keeps one hand behind his or her back. Why?
> What average force is necessary to bring a 50.0 kg sled from rest to a speed of 3.0 m/s in a period of 20.0 s? Assume frictionless ice.
> While I1 is increasing, does current flow in loop 2? If so, does it flow clockwise or counterclockwise as viewed from the right? Explain.
> A packing carton slides down an inclined plane of angle 30.0° and of incline length 2.0 m. (a) If the initial speed of the carton is 4.0 m/s directed down the incline, what is the speed at the bottom? Ignore friction. (b) How long does it take the cart
> Verify that the collision between the proton and the nitrogen nucleus in Example 26.4 is elastic.
> A dentist holds a small mirror 1.9 cm from a surface of a patient's tooth. The image formed is upright and 5.0 times as large as the object. (a) Is the image real or virtual? (b) What is the focal length of the mirror? Is it concave or convex? (c) If
> A beam of neutrons is used to study molecular structure through a series of diffraction experiments. A beam of neutrons with a wide range of de Broglie wavelengths comes from the core of a nuclear reactor. In a time-offlight technique, used to select neu
> Refer to the pulse in Problem 9. (a) What is the speed of propagation of the pulse? (b) At what average speed does the point at x = 2.0 m move during this time interval?
> You decide to test your physics knowledge while going over a waterfall in a barrel. You take a baseball into the barrel with you, and as you are falling vertically downward, you let go of the ball. What do you expect to see for the motion of the ball rel
> The activity of a sample containing radioactive 108Ag is 6.4 × 104 Bq. Precisely 12 min later, the activity is 2.0 × 103 Bq. Calculate the half-life of 108Ag.
> A lens (n = 1.52) is coated with a magnesium fluoride film (n = 1.38). (a) If the coating is to cause destructive interference in reflected light for λ = 560 nm (the peak of the solar spectrum), what should its minimum thickness be? (b) At what two wav
> In an accelerator, two protons with equal kinetic energies collide head-on. The following reaction takes place: . What is the minimum possible kinetic energy of each of the incident proton beams?
> The magnetic flux through a flat surface is known. The area of the surface is also known. Is that information enough to calculate the average magnetic field on the surface? Explain.
> During a walk on the Moon, an astronaut accidentally drops his camera over a 20.0 m cliff. It leaves his hands with zero speed, and after 2.0 s it has attained a velocity of 3.3 m/s downward. How far has the camera fallen after 4.0 s?
> Is it more dangerous to touch a “live” electric wire when your hands are dry or wet, everything else being equal? Explain.
> Questions 1–4: A satellite in orbit travels around Earth in uniform circular motion. In the figure, the satellite moves counterclockwise (ABCDA). Answer choices: (a) +x (b) +y (c) −x (d) −y (e) 45&Aci
> The photoelectric effect is studied using a tungsten target. The work function of tungsten is 4.5 eV. The incident photons have energy 4.8 eV. (a) What is the threshold frequency? (b) What is the stopping potential? (c) Explain why, in classical physi
> Why are astronomical observatories often located on mountaintops?
> Why are ammeters connected in series with a circuit element in which the current is to be measured and voltmeters connected in parallel across the element for which the potential difference is to be measured?
> When helium weather balloons are released, they are purposely underinflated. Why? [Hint: The balloons go to very high altitudes.]
> An object hanging vertically from a spring and a simple pendulum both have a period of oscillation of 1 s on Earth. An astronaut takes the two devices to another planet where the gravitational field is stronger than that of Earth. For each of the two sys
> The rogue starship Galaxa is being chased by the battle cruiser Millenia. The Millenia is catching up to the Galaxa at a rate of 0.55c when the captain of the Millenia decides it is time to fire a missile. First the captain shines a laser range finder to
> One cold and windy winter day, Zach notices a humming sound coming from his chimney, which is open at the top and closed at the bottom. He opens the chimney at the bottom and notices that the sound changes. He goes over to the piano to try to match the n
> Is the electric field inside a conductor always zero? If not, when is it not zero? Explain.
> If E = 0 everywhere throughout a region of space, what do we know is true about the potential at points in that region?
> 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. When a car is going 20.0 m/s on this curve, what minimum coefficient of static friction is needed if the car is to navigate the cur
> A sound wave of frequency 1231 Hz travels through air directly toward a wall, then through the wall out into air again. If the initial speed of the sound wave is 341 m/s and its speed in the wall is 620 m/s, what are (a) the initial wavelength of the so
> An object is placed on a scale. Under what conditions does the scale read something other than the object's weight, even though the scale is functioning properly and is calibrated correctly? Explain.
> Can the average speed and the magnitude of the average velocity ever be equal? If so, under what circumstances?
> For divers going to great depths, the composition of the air in the tank must be modified. The ideal composition is to have approximately the same number of O2 molecules per unit volume as in surface air (to avoid oxygen poisoning), and to use helium ins
> On a graph of vx versus time, what quantity does the area under the graph represent?
> The columns built by the ancient Greeks and Romans to support temples and other structures are tapered; they are thicker at the bottom than at the top. This certainly has an aesthetic purpose, but is there an engineering purpose as well? What might it be
> You are driving your car along a country road at a speed of 27.0 m/s. As you come over the crest of a hill, you notice a farm tractor 25.0 m ahead of you on the road, moving in the same direction as you at a speed of 10.0 m/s. You immediately slam on you
> Verify that the units of the rotational form of Newton's second law [Eq. (8-19)] are consistent. In other words, show that the product of a rotational inertia expressed in kg·m2 and an angular acceleration expressed in rad/s2 is a torque expressed in N·m
> An electron moving in the positive x-direction passes through a slit of width Δy = 85 nm. What is the minimum uncertainty in the electron's velocity in the y-direction?
> While testing speakers for a concert, Tomás sets up two speakers to produce sound waves at the same frequency, which is between 100 Hz and 150 Hz. The two speakers vibrate in phase with each other. He notices that when he listens at certain locations, th
> Two identical circular coils of wire are separated by a fixed center-to- center distance. Describe the orientation of the coils that would (a) maximize or (b) minimize their mutual inductance.
> Two loops of wire are next to each other in the same plane. (a) If the switch S is closed, does current flow in loop 2? If so, in what direction? (b) Does the current in loop 2 flow for only a brief moment, or does it continue? (c) Is there a magnetic
> What is the de Broglie wavelength of a proton with kinetic energy 1.0 TeV?
> An object moves in the positive x-direction under the influence of a force Fx. A graph of Fx versus vx is shown. (a) What is the instantaneous power (i.e., the rate at which the force does work on the object) when its speed is 10 m/s? (b) What is the i
> Objects that are at rest relative to Earth’s surface are in circular motion due to Earth’s rotation. What is the radial acceleration of an African baobab tree located at the equator?
> If E = 0 at a single point, then a point charge placed at that point will feel no electric force. What does it mean if the potential is zero at a point? Are there any assumptions behind your answer?
> 21. A stone is thrown at an angle of 20° below the horizontal from the top of a cliff. Assume no air resistance. One second after being thrown, the stone's velocity is at angle θ below the horizontal. Which is true? (a) θ = 0 (b) θ = 20° (c) 0 < θ < 20°
> Why are all parts of a conductor at the same potential in electrostatic equilibrium?
> Coherent green light with a wavelength of 520 nm and coherent violet light with a wavelength of 412 nm are incident on a double slit with slit separation of 0.020 mm. The interference pattern is displayed on a screen 72.0 cm away. (a) Find the separatio
> An electron in an atom has an angular momentum quantum number of 2. (a) What is the magnitude of the angular momentum of this electron in terms of ħ? (b) What are the possible values for the z- components of this electron's angular momentum? (c) Draw a
> Magnetic induction is the principle behind the operation of mechanical speedometers used in automobiles and bicycles. In the drawing, a simplified version of the speedometer, a metal disk is free to spin about the vertical axis passing through its center
> An electron is accelerated from rest through a potential difference ΔV. If the electron reaches a speed of 7.26 × 106 m/s, what is the potential difference? Be sure to include the correct sign. (Does the electron move through an increase or a decrease in
> Objects that are at rest relative to Earth’s surface are in circular motion due to Earth’s rotation. What is the radial acceleration of a painting hanging in the Prado Museum in Madrid, Spain, at a latitude of 40.2&Aci
> A point charge moves to a region of higher potential and yet the electric potential energy decreases. How is this possible?
> At the Stanford Linear Accelerator, electrons and positrons collide together at very high energies to create other elementary particles. Suppose an electron and a positron, each with rest energies of 0.511 MeV, collide to create a proton (rest energy 938
> In the United States, the ac household current oscillates at a frequency of 60 Hz. In the time it takes for the current to make one oscillation, how far has the electromagnetic wave traveled from the current- carrying wire? This distance is the wavelengt
> A circular conducting loop with radius 1.8 cm is placed in a uniform magnetic field of 0.88 T with the plane of the coil perpendicular to the magnetic field as shown. The magnetic field decreases to 0.36 T in a time interval of 29 ms. What is the average
> A parallel plate capacitor has a capacitance of 2.0 µF and plate separation of 1.0 mm. (a) How much potential difference can be placed across the capacitor before dielectric breakdown of air occurs (Emax = 3 × 106 V/m)? (b) What is the magnitude of the
> Points A and B are at the same potential. What is the total work that must be done by an external agent to move a charge from A to B? Does your answer mean that no external force need be applied? Explain.
> A charged particle is accelerated from rest through a potential difference ΔV. The particle then passes straight through a velocity selector (field magnitudes E and B). Derive an expression for the charge-to-mass ratio (q/m) of the particle in terms of Δ
> What are some of the advantages of using mirrors rather than lenses for astronomical telescopes?
> 11. A woman stands on a bathroom scale in an elevator that is not moving. The scale reads 500 N. The elevator then moves downward at a constant velocity of 4.5 m/s. What does the scale read while the elevator descends with constant velocity? (a) 100 N (b
> In a reciprocating saw, a Scotch yoke converts the rotation of the motor into the back-and-forth motion of the blade. The Scotch yoke is a mechanical device used to convert oscillatory motion to circular motion or vice versa. A wheel with a fixed knob ro
> The motion of a simple pendulum is approximately SHM only if the amplitude is small. Consider a simple pendulum that is released from a horizontal position (θi = 90° in Fig. 10.23). (a) Using conservation of energy, find the speed of the pendulum bob at
> The f-stop of a camera lens is defined as the ratio of the focal length of lens to the diameter of the aperture. A large f-stop therefore means a small aperture. If diffraction is the only consideration, would you use the largest or the smallest f-stop t
> An object is subjected to two constant forces that are perpendicular to each other. Can a set of x- and y-axes be chosen so that the acceleration of the object has only one nonzero component? If so, how? Explain.
> Suppose some astronauts have landed on Mars. When the astronauts ask a question of mission control personnel on Earth, what is the shortest possible time they have to wait for a response? The average distance from Mars to the Sun is 2.28 × 1011 m.
> Two sheets of ideal polarizing material are placed with their transmission axes at right angles to each other. A third polarizing sheet is placed between them with its transmission axis at 45° to the axes of the other two. (a) If unpolarized light of in
> Four long straight wires, each with current I, overlap to form a square with side 2r. (a) Find the magnetic field at the center of the square. (b) Compare your answer with the magnetic field at the center of a circular loop of radius r carrying current
