Question: Can static friction do work? If so,

> Five ideal mass-spring systems are described by their masses, spring constants, and amplitudes of oscillation as follows. Rank them in decreasing order of the frequency of oscillations. (a) mass m, spring constant k, amplitude A (b) mass 2m, spring con

> Part (a) of the figure shows a simplified model of how the triceps muscle connects to the forearm. As the angle θ is changed, the tendon wraps around a nearly circular arc. Explain how this is much more effective than if the tendon is connec

> A 4.0 kg block is released from rest at the top of a frictionless plane of length 8.0 m that is inclined at an angle of 15° to the horizontal. A cord is attached to the block and trails along behind it. When the block reaches a point 5.0 m alo

> In Fig. 8.2b, where should the doorknob be located to make the door easier to open?

> In your own words, phrase each of Newton's three laws of motion as a statement about momentum.

> A refracting telescope is 36.4 cm long and has a 6.0 cm diameter aperture. The magnifying power is 90.0. (a) What are the focal lengths of the lenses? (b) What is the diffraction limit on the minimum angular separation of objects that the telescope can

> Sonya is designing a diffraction experiment for her students. She has a laser that emits light of wavelength 627 nm and a grating with a distance of 2.40 × 10−3 mm between slits. She hopes to shine the light through the grating and display a total of nin

> In a uniform electric field of magnitude E, the field lines cross through a rectangle of area A at an angle of 60.0° with respect to the plane of the rectangle. What is the flux through the rectangle?

> Two cars, each of mass 1300 kg, are approaching each other on a head-on collision course. Each speedometer reads 19 m/s. What is the magnitude of the total momentum of the system?

> What is the tension in the string when the ball hangs straight down at rest?

> Many home heating systems operate by pumping hot water through radiator pipes. The flow of the water to different “zones” in the house is controlled by zone valves that open in response to thermostats. The opening and

> A radioactive nucleus is at rest when it spontaneously decays by emitting an electron and neutrino. The momentum of the electron is 8.20 × 10−19 kg·m/s, and it is directed at right angles to that of the neutri

> Mary and Daryl are new to the sport of rock climbing. Mary says she wants a stiff rope because a stiff rope is a strong rope. Daryl insists that a good climbing rope must have some stretch. Who is correct, and why?

> Which would be more effective: a hammer that collides elastically with a nail, or one that collides perfectly inelastically? Assume that the mass of the hammer is much larger than that of the nail.

> An astronaut hits a golf ball on the surface of the Moon. Is the momentum of the ball conserved while it is in flight? Is there a component of its momentum that is conserved?

> An astronaut in deep space is taking a space walk when the tether connecting him to his spaceship breaks. How can he get back to the ship? He doesn't have a rocket propulsion backpack, unfortunately, but he is carrying a big wrench.

> The particle in a box model is often used to make rough estimates of energy level spacings. Suppose that you have a proton confined to a one-dimensional box of length equal to a nuclear diameter (about 10−14 m). (a) What is the energy difference between

> A plane weighing 220 kN (25 tons) lands on an aircraft carrier. The plane is moving horizontally at 67 m/s (150 mi/h) when its tailhook grabs hold of the arresting cables. The cables bring the plane to a stop in a distance of 84 m. (a) How much work is

> A firecracker at rest explodes, sending fragments off in all directions. Initially the firecracker has zero momentum, but after the explosion the fragments flying off each have quite a lot of momentum. Hasn't momentum been created? If not, explain why no

> Figure 17.31b shows a thundercloud before a lightning strike has occurred. The bottom of the thundercloud and Earth's surface might be modeled as a charged parallel plate capacitor. The base of the cloud, which is roughly parallel to Earth's surface, ser

> If you take a rifle and saw off part of the barrel, the muzzle speed (the speed at which bullets emerge from the barrel) will be smaller. Why?

> A force of 30 N is applied for 5 s to each of two objects of different masses. (a) Which one has the greater momentum change? (b) The greater velocity change? (c) The greater acceleration?

> Micah is standing on his frictionless skateboard facing a concrete wall. He wants to project himself backward by throwing small balls at the wall. His friend Jeremy says that Micah need not throw the balls against the wall, he just needs to throw the bal

> A lambda particle (Λ) decays at rest to a proton and pion through the reaction Λ → p + π−. The rest energies of the particles are: Λ, 1115.7 MeV; p, 938.3 MeV; and π−, 139.6 MeV. Use conservation of energy and momentum to determine the kinetic energies o

> At an antique car rally, a Stanley Steamer automobile travels north at 40 km/h and a Pierce Arrow automobile travels east at 50 km/h. Relative to an observer riding in the Stanley Steamer, what are the x- and y-components of the velocity of the Pierce Ar

> Two parallel plates are 4.0 cm apart. The bottom plate is charged positively and the top plate is charged negatively, producing a uniform electric field of 5.0 × 104 N/C in the region between the plates. What is the time required for an electron, which s

> A planet with a radius of 6.00 × 107 m has a gravitational field of magnitude 30.0 m/s2 at the surface. What is the escape speed from the planet?

> A baseball batting coach emphasizes the importance of “follow- through” when a batter is trying for a home run. The coach explains that the follow-through keeps the bat in contact with the ball for a longer time so the ball will travel a greater distance

> An ideal spring has a spring constant k = 20.0 N/m. What is the amount of work that must be done to stretch the spring 0.40 m from its relaxed length?

> In the “executive toy,” two balls are pulled back and then released. After the collision, two balls move away on the opposite side. Why do we never see three balls move away following this action, although with a lower

> Two coherent sound waves have intensities of 0.040 W/m2 and 0.090 W/m2 where you are listening. (a) If the waves interfere constructively, what is the intensity that you hear? (b) What if they interfere destructively? (c) If they were incoherent, what

> In an egg toss, two people try to toss a raw egg back and forth without breaking it as they move farther and farther apart. Discuss a strategy in terms of impulse and momentum for catching the egg without breaking it.

> The momentum of a system can only be changed by an external force. What is the external force that changes the momentum of a bicycle (with its rider) as it speeds up, slows down, or changes direction? Is it true that changes in the bicycle's kinetic ener

> A top fuel drag racer with a mass of 500.0 kg completes a quarter- mile (402 m) drag race in a time of 4.2 s starting from rest. The car’s final speed is 125 m/s. What is the engine’s average power output? Ignore friction and air resistance.

> A woman is 1.60 m tall. When standing straight, is her CM necessarily 0.80 m above the floor? Explain.

> Two solenoids, of N1 and N2 turns respectively, are wound on the same form. They have the same length â„“ and radius r. (a) If an ac current flows in solenoid 1 (N1 turns), write an expression for the total flux through solenoid 2 as a f

> Two objects with different masses have the same kinetic energy. Which has the larger magnitude of momentum?

> An airplane has a velocity relative to the ground of 210 m/s toward the east. The pilot measures his airspeed (the speed of the plane relative to the air) to be 160 m/s. What is the minimum wind velocity possible?

> You are trapped on the second floor of a burning building. The stairway is impassable, but there is a balcony outside your window. Describe what might happen in the following situations. (a) You jump from the second-story balcony to the pavement below,

> (a) Find the electric flux through each side of a cube of edge length a in a uniform electric field of magnitude E. The field direction is perpendicular to two of the faces. (b) What is the total flux through the cube?

> (a) Calculate the net electric force acting on the dipole. (b) Show that the magnitude of the torque on the dipole is τ = qEd sin θ. (c) Calculate the torque acting on the dipole for θ = 0, 36.9°, and 90.0°.

> A cheetah can accelerate from rest to 24 m/s in 2.0 s. Assuming the acceleration is constant over the time interval, (a) what is the magnitude of the acceleration of the cheetah? (b) What is the distance traveled by the cheetah in these 2.0 s? (c) A r

> A bicycle rider notices that he is approaching a steep hill. Explain, in terms of energy, why the bicyclist pedals hard to gain as much speed as possible on level road before reaching the hill.

> A gymnast is swinging in a vertical circle about a crossbar. In terms of energy conservation, explain why the speed of the gymnast’s body is slowest at the top of the circle and fastest at the bottom.

> When a ball is dropped to the floor from a height h, it strikes the ground and briefly undergoes a change of shape before rebounding to a maximum height less than h. Explain why it does not return to the same height h.

> A roller coaster car (mass = 988 kg including passengers) is about to roll down a track. The diameter of the circular loop is 20.0 m and the car starts out from rest 40.0 m above the lowest point of the track. Ignore friction and air resistance. (a) At

> A green laser has a wavelength of 532 nm. A grating and a lens are used to split the beam into three parallel beams spaced 1.85 cm apart. (a) What range of slit spacings can the grating have to produce three and only three beams? (b) If the slit spacing

> The field between the plates of a parallel plate capacitor, E = Q/(ϵ0A), is due to the superposition of equal contributions from the charges on the two plates. Therefore, each plate exerts an electric force on the other. (a) Find the magnitude of this f

> In the design of a roller coaster, is it possible for any hill of the ride to be higher than the first one? If so, how?

> A car is driving directly north on the freeway at a speed of 110 km/h, and a truck is leaving the freeway driving 85 km/h in a direction that is 35° west of north. What is the velocity of the truck relative to the car?

> The period of oscillation of an object in an ideal spring-and-mass system is 0.50 s and the amplitude is 5.0 cm. What is the speed at the equilibrium point?

> A copper washer is to be fit in place over a steel bolt. Both pieces of metal are at 20.0°C. If the diameter of the bolt is 1.0000 cm and the inner diameter of the washer is 0.9980 cm, to what temperature must the washer be raised so it will fit over the

> A mango falls to the ground. During the fall, does Earth’s gravitational field do positive or negative work Wm on the mango? Does the mango’s gravitational field do positive or negative work WE on Earth? Compare the signs and the magnitudes of Wm and WE.

> Why do roads leading to the top of a mountain have switchbacks that wind back and forth? [Hint: Think of the road as an inclined plane.]

> An infinitely long conducting cylinder sits near an infinite conducting sheet (side view in the diagram). The cylinder and sheet have equal and opposite charges; the cylinder is positive. (a) Sketch some electric field lines. (b) Sketch some equipotent

> You are standing on a balcony overlooking the beach. You throw a ball straight up into the air with speed vi and throw an identical ball straight down with speed vi. Ignoring air resistance, how do the speeds of the balls compare just before they hit the

> Why might an elevator cable break during acceleration when lifting a lighter load than it normally supports at rest or at constant velocity?

> If air resistance is ignored, what force(s) act on an object in free fall?

> An ideal transformer takes an ac voltage of amplitude 170 V as its input and supplies a 7.8 V amplitude to a circuit that converts it to dc. The primary has 300 turns. (a) How many turns does the secondary have? (b) When the circuit uses a power of 5.0

> If the trajectory is parabolic in one reference frame, is it always, never, or sometimes parabolic in another reference frame that moves at constant velocity with respect to the first reference frame? If the trajectory can be other than parabolic, what e

> What is the acceleration of an object thrown straight up into the air at the highest point of its motion? Does the answer depend on whether air resistance is negligible or not? Explain.

> Is it possible for two identical projectiles with identical initial speeds, but with two different angles of elevation, to land in the same spot? Explain. Ignore air resistance and sketch the trajectories.

> A large parallel plate capacitor with air between the plates has plate separation 1.00 cm and plate area 314 cm2. The capacitor is connected to a 20.0 V battery and then disconnected. How much work is done on the capacitor as the plate separation is incr

> A Nile cruise ship takes 20.8 h to go upstream from Luxor to Aswan, a distance of 208 km, and 19.2 h to make the return trip downstream. Assuming the ship’s speed relative to the water is the same in both cases, calculate the speed of the current in the

> How much work is done on the bowstring of Example 6.9 to draw it back by 20.0 cm? [Hint: Rather than recalculate from scratch, use proportional reasoning.]

> You are on the Moon and would like to send a probe into space so that it does not fall back to the surface of the Moon. What launch speed do you need?

> Each prong of a vibrating tuning fork moves back and forth quite precisely in simple harmonic motion. The distance the prong moves between its extreme positions is 2.24 mm. If the frequency of the tuning fork is 440.0 Hz, what are the maximum velocity an

> A proton in Fermilab's Tevatron is accelerated through a potential difference of 2.5 MV during each revolution around the ring of radius 1.0 km. In order to reach an energy of 1 TeV, how many revolutions must the proton make? How far has it traveled?

> A flat-bottomed barge, loaded with coal, has a mass of 3.0 × 105 kg. The barge is 20.0 m long and 10.0 m wide. It floats in freshwater. What is the depth of the barge below the waterline?

> Why is the muzzle of a rifle not aimed directly at the center of the target? Why is this more important at longer ranges?

> A spacecraft is in orbit around Jupiter. The radius of the orbit is 3.0 times the radius of Jupiter (which is RJ = 71 500 km). The gravitational field at the surface of Jupiter is 23 N/kg. What is the period of the spacecraft’s orbit? [Hint: You don’t ne

> Give a real example of the motion of some object for which: (a) the velocity and net force are in the same direction; (b) the velocity and net force are in opposite directions; (c) the velocity is nonzero and the net force is zero; (d) the velocity a

> While you are supervising playground activity during recess, the children are playing a game of tag. As Marlene and Shelly run past each other in opposite directions, Marlene reaches out and touches the shiny logo on Shelly’s jacket. Shelly starts to cry

> What is the potential energy if a third point charge q = −4.2 nC is placed at point a?

> You are given the task of designing a mechanism to trip a switch in an automobile seat belt, causing it to tighten in case of an accident. You decide that if the velocity of the car is high and constant the passenger is in no danger; it is only high acce

> Tell whether each of the following objects has a constant velocity and explain your reasoning. (a) A car driving around a curve at constant speed on a flat road. (b) A car driving straight up a 6° incline at constant speed. (c) The Moon in orbit aroun

> The mass of 1 mol of 13C (carbon-13) is 13.003 g. (a) What is the mass in u of one 13C atom? (b) What is the mass in kilograms of one 13C atom?

> What tool enabled scientists to create hundreds of different hadrons in the latter half of the twentieth century?

> If an object is acted on by two constant forces is it possible for the object to move at constant velocity? If so, what must be true about the two forces? Give an example.

> 31 to 33. Each row of the table describes an object moving along the x-axis. Based on the information given in two of the columns, choose the correct entry for the other columns. The question number is in parentheses. 34. A sailor climbs the mast in a b

> If an object is acted on by a single constant force, is it possible for the object to remain at rest? Is it possible for the object to move with constant velocity? Is it possible for the object’s speed to be decreasing? Is it possible for it to change di

> You have a simple pendulum and a mass-spring system in which the mass oscillates vertically. They both oscillate with the same period T. You take them both to the surface of the Moon, where the gravitational field is 1/6 that of Earth. (a) Is the period

> The seat on a carnival ride is fixed on the end of an 8.0 m long beam, pivoted at the other end. If the beam sweeps through an angle of 120°, what is the distance through which the rider moves?

> A sewing machine needle moves with a rapid vibratory motion, rather like SHM, as it sews a seam. Suppose the needle moves 8.4 mm from its highest to its lowest position and it makes 24 stitches in 9.0 s. What is the maximum needle speed?

> A parallel plate capacitor has a charge of 5.5 × 10−7 C on one plate and −5.5 × 10−7 C on the other. The distance between the plates is increased by 50% while the charge on each plate stays the same. What happens to the energy stored in the capacitor?

> Anthony is going to drive a flat-bed truck up a hill that makes an angle of 10° with respect to the horizontal direction. A 36.0 kg package sits in the back of the truck. The coefficient of static friction between the package and the truck bed is 0.380.

> 21. The four graphs show vx versus time. Which graph shows a changing ax that is always positive? 22. A boy plans to paddle a rubber raft across a river to the east bank while the current flows down river from north to south at 1 m/s. He is able to padd

> Using Newton’s laws, explain why a cord must exert forces of equal magnitude on the objects attached to each end, assuming that the cord’s mass is negligibly small.

> You are driving a car through campus when a fellow student steps out in front of you. You slam on the brakes, creating a 9.0 m long skid mark as measured by the police officer standing on the corner. She also has a device that measures the coefficient of

> 11. What is the average velocity of the jogger during the 30.0 min? (a) 1.3 m/s, north (b) 1.7 m/s, north (c) 2.1 m/s, north (d) 2.9 m/s, north 12. What is the average speed of the jogger for the 30 min? (a) 1.4 m/s (b) 1.7 m/s (c) 2.1 m/s (d) 2.9 m/s

> A person climbs from a Paris metro station to the street level by walking up a stalled escalator in 94 s. It takes 66 s to ride the same distance when standing on the escalator when it is operating normally. How long would it take for him to climb from t

> Refer to Conceptual Question 17 in Chapter 2. A heavy lead ball hangs from a string attached to a sturdy wooden frame. A second string is attached to a hook on the bottom of the lead ball. In Chapter 2, you imagined pulling slowly and steadily on the low

> 1. The term force most accurately describes (a) the mass of an object. (b) the inertia of an object. (c) the quantity that causes displacement. (d) the quantity that keeps an object moving. (e) the quantity that changes the velocity of an object. 2. A s

> Name a situation in which the speed of an object is constant while the velocity is not.

> A copper wire has a resistance of 24 Ω at 20°C. An aluminum wire has 3.0 times the length and 2.0 times the radius of the copper wire. (a) What is the resistance of the aluminum wire at 20°C? (b) The graph show

> What is the maximum electric energy density possible in dry air without dielectric breakdown occurring?

> An RLC series circuit has a resistance of R = 325 Ω, an inductance L = 0.300 mH, and a capacitance C = 33.0 nF. (a) What is the resonant frequency? (b) If the capacitor breaks down for peak voltages in excess of 7.0 × 102 V, what is the maximum source

> A horizontal towrope exerts a force of 240 N due west on a water- skier while the skier moves due west a distance of 54 m. How much work does the towrope do on the water-skier?

> A compass is placed directly on top of a wire (needle not shown). The current in the wire flows to the right. Which way does the north end of the needle point? Explain. (Ignore Earth's magnetic field.)

> A positively charged rod is brought near two uncharged conducting spheres of the same size that are initially touching each other (diagram a). The spheres are moved apart, and then the charged rod is removed (diagram b). (a) What is the sign of the net