16 Created by Master Student Physics Practice Test #7 1 / 40 Some opera singers are able to use their voice to shatter a crystal glass. They can do this because of acoustic reflection. multiple echoes. interference. resonance. beats. The correct answer is (D). If the input frequency of a wave system is equal to its vibrating frequency, the resonant system acts to amplify the waves, thus transferring their energy into the delicate crystal and breaking it. 2 / 40 When a gas undergoes an adiabatic expansion, its energy increases. pressure increases. volume decreases. temperature increases. temperature decreases. The correct answer is (E). An adiabatic expansion is a process in which no heat flows into or out of the system. During an adiabatic expansion the gas cools as it expands and does work. 3 / 40 An object of mass 0.5 kg, moving in a circular path of radius 0.25 m, experiences a centripetal acceleration of constant magnitude 9 m/s2. What is the object's angular speed? 2.3 rad/s 4.5 rad/s 6 rad/s 12 rad/s Cannot be determined from the information given By combining the equation for centripetal acceleration, ac = v2/r, with v = rω, we find 4 / 40 What is the wavelength of a wave with period 2 s and speed 2 cm/s ? 0.25 cm 0.5 cm 1 cm 2 cm 4 cm From the equations λf = v and f = I/T, we get λ = vT = 2(cm/s)(2 s) = 4 cm. 5 / 40 A pendulum swings at a rate of .75 vibration/ sec. Which of the following changes could be made to the pendulum to cause the period of the pendulum to increase? Mass of the bob was increased Length of the pendulum was increased Mass of the bob was decreased Length of the pendulum was decreased The material from which the pendulum bob was made The correct answer is (B). An increase in the length of the pendulum causes the period of the pendulum to increase too. . Notice the in the period equation. 6 / 40 What would happen to the electrostatic force between a pair of charged particles if both charges were doubled and the distance between them were also doubled? It would decrease by a factor of 4. It would decrease by a factor of 2. It would remain unchanged. It would increase by a factor of 2. It would increase by a factor of 4. Applying Coulomb's law, we see that the electric force will not change. 7 / 40 A mass is suspended by a rubber band. The rubber band is stretched by the weight of the mass, but it is not moving. The action force that causes the rubber band to stretch comes from the earth. What is the reaction force of the force pair? The rubber band pulling on the mass The rubber band pulling on the earth The mass pulling on the rubber band The mass pulling on the earth The earth pulling on the rubber band The correct answer is (D). According to Newton's Third Law, the action-reaction force pair must be equal in magnitude and oppositely directed. The earth pulls on the mass, and the mass pulls on the earth (the pair) with the same force. 8 / 40 A step down transformer changes the high input voltage used in our houses (120V) into the low voltage used to charge an electric razor (24V). What must be the ratio of the turns of wire from the primary side of the transformer to the secondary side? 5:01 2:7 1:8 2:9 1:10 The correct answer is (A). The ratio between the number of turns in the primary and the number of turns in the secondary is equal to the ratio of the primary voltage and the secondary voltage 120V/24V = 5:1. 9 / 40 Golden Glove boxers, who are amateurs, use larger, more padded gloves than professional boxers use. The amateur boxers are more protected from injury because the larger glove exerts more energy on the boxer. the larger glove increases time of impact on the boxer. the larger glove increases the power exerted on the boxer. the larger glove exerts a larger impulse on the boxer. the larger glove exerts a larger force on the boxer. The correct answer is (D). The larger amount of padding in the amateur gloves causes the time of impact to be increased, which results in less force being exerted. 10 / 40 The reason an observer cannot detect the wave nature of a fast moving truck is the momentum of the truck is too large. the velocity of the wave is too large. there are no waves to be detected. the frequency is too low. the wavelengths are too small. The correct answer is (D). The de Broglia wavelength cannot be detected because the objects in question have velocities that are too small for the waves they create to be detectable. 11 / 40 A pair of a particles (helium nuclei) approach one another head on. Compared to the force they exert on one another at a distance of .066 m, by how much will the force the two particles exert on one another at .033 mm increase? 2 3 4 6 8 The correct answer is (C). According to Coulomb's law, the force exerted by two charged bodies on one another is indirectly related to the square of the distance between them. When the distance is halved, they exert four times more force on one another. 12 / 40 The first law of thermodynamics is a restatement of Guy-Lassac's Law. the principle of entropy. the principle of enthalpy. conservation of energy. Avogadro's hypothesis. The correct answer is (D). The first law of thermodynamics can be stated as: 13 / 40 While standing in front of a plane flat mirror and looking at yourself, you raise your right hand. Which is the best description of the image you see? Erect and enlarged Erect and reduced Erect and reversed Inverted and reversed Inverted and reduced The correct answer is (C). Your image is standing upright. Your feet and the image of your feet are down, and your head and the image of your head are up. When you raise your right hand, the left hand of the image is raised. This is a reversal of left and right. 14 / 40 A large object is placed at exactly 55% of the distance to the moon from the earth. Eventually the object will fall to the sun. fall to the moon. fall to the earth. remain in the same place. drift out of the solar system. The correct answer is (C). The moon is only 1/6 the size of the earth, so at a distance 55% of the way to the moon, the object is still under the influence of the earth's gravitational field. That means the object will eventually fall back to the earth. 15 / 40 Which of the following best describes the magnetic field lines created by a long, straight, current-carrying wire? Rays that emanate from the wire Circles centered on the wire Lines parallel to the wire Lines perpendicular to the wire Noncircular ellipses centered on the wire The magnetic field lines created by a long, straight, current-carrying wire are circles centered on the wire. 16 / 40 A photon of light from which of the following electromagnetic radiations carries the greater amount of energy? Blue Green Orange Red Yellow The correct answer is (A). The higher the frequency of the light waves, the higher the energy of the photons. Of the choices presented, blue light has the highest frequency. 17 / 40 Lead-199 has a half-life of 1.5 hours. If a researcher begins with 2 grams of lead-199, how much will remain after 6 hours? 0.125 grams 0.25 grams 0.375 grams 0.5 grams 0.625 grams Because each half-life is 1.5 hours, a time interval of 6 hours is equal to 4 half-lives. After each half-life elapses, the mass of the sample is cut in half, so after 4 half-lives, the mass of the sample decreases from 2 grams to 1 gram to 0.5 grams to 0.25 grams and, finally, to 0.125 grams. 18 / 40 A team of skydivers jumps from a plane and holds hands to form a flower-like design. As the skydivers begin their free fall, their velocity increases and their acceleration increases. acceleration decreases. acceleration is constant. acceleration is zero. air resistance is reduced. The correct answer is (B). The acceleration of the skydivers continues to decrease until the terminal velocity of the group is reached. When the air resistance reaches the point where it exactly balances the force exerted on the divers by the earth's gravitational attraction, their acceleration becomes zero. 19 / 40 A mover, exerting a steady force of 200 N, pushes a box of mass 50 kg across a flat wooden floor. If the velocity of the box does not change while he pushes, what is the coefficient of kinetic friction between the box and the floor? 0.2 0.4 0.5 0.6 0.8 Since the velocity does not change, the acceleration of the box is zero, so the net force the box feels must also be zero. Since the mover pushes on the box with a force of 200 N, the force of kinetic friction must also be 200 N (in the opposite direction) to give a net force of zero. Because the strength of the force of kinetic friction, Ffriction, is equal to μFN, where FN = mg (since the floor is flat), we find that 20 / 40 In an experiment designed to study the photoelectric effect, it is observed that low-intensity visible light of wavelength 550 nm produced no photoelectrons. Which of the following best describes what would occur if the intensity of this light were increased dramatically? Almost immediately, photoelectrons would be produced with a kinetic energy equal to the energy of the incident photons. Almost immediately, photoelectrons would be produced with a kinetic energy equal to the energy of the incident photons minus the work function of the metal. After several seconds, necessary for the electrons to absorb sufficient energy from the incident energy, photoelectrons would be produced with a kinetic energy equal to the energy of the incident photons. After several seconds, necessary for the electrons to absorb sufficient energy from the incident energy, photoelectrons would be produced with a kinetic energy equal to the energy of the incident photons minus the work function of the metal. Nothing would happen. If the photons of the incident light have insufficient energy to liberate electrons from the metal's surface, then simply increasing the number of these weak photons (that is, increasing the intensity of the light) will do nothing. To produce photoelectrons, each photon of the incident light must have an energy at least as great as the work function of the metal. 21 / 40 The choices below give a description of the quantities listed above. Match the statement below with the quantity it describes above. The product of the frequency and the wavelength. Frequency Amplitude Wavelength Velocity Period The correct answer is (D). The product of the frequency and the wavelength can be obtained by the dimensional analysis. V = λf , which yields 22 / 40 Two 1 liter containers contain 1 mole each of the same gas at the same temperature. Container A is allowed to expand until the temperature of gas A is reduced by half. Container B is compressed until the temperature of gas B doubles. Both gases are then mixed together in a 2 liter container. Which of the following statements about the gases is correct? Both gases gain heat. Both gases lose heat. Gas A loses heat to gas B. Gas B loses heat to gas A. The equilibrium temperature of the gases is exactly one half the original starting temperature of the gases. The correct answer is (D). According to the first law of thermodynamics, the internal heat of the system remains the same unless work is done or heat is added to the system. Neither of those two things occurs, so the system of two objects, one hot and one cold, transfers heat between itself with the hot object losing to the cold object until thermal equilibrium is reached. 23 / 40 Geosynchronous satellites remain over the same spot on the earth's surface because they orbit the earth every 24 hours. are in polar orbits. rotate opposite the earth's rotational direction. have a varying orbital height. use terrain reading technology to remain on station. The correct answer is (A). The geosynchronous satellite circles the earth at the same rate as the earth turns beneath it. Thus the satellite stays in the same position relative the earth. 24 / 40 A crate of mass 100 kg is at rest on a horizontal floor. The coefficient of static friction between the crate and the floor is 0.4, and the coefficient of kinetic friction is 0.3. A force F of magnitude 344 N is then applied to the crate, parallel to the floor. Which of the following is true? The crate will accelerate across the floor at 0.5 m/s2. The static friction force, which is the reaction force to F as guaranteed by Newton's third law, will also have a magnitude of 344 N. The crate will slide across the floor at a constant speed of 0.5 m/s. The crate will not move. None of the above The maximum force that static friction can exert on the crate is μsFN = μsFw = μs mg = (0.4)(100 kg)(10 N/kg) = 400 N. Since the force applied to the crate is only 344 N, static friction is able to apply that same magnitude of force on the crate, keeping it stationary. [B is incorrect because the static friction force is not the reaction force to F; both F and Ff (static) act on the same object (the crate) and therefore cannot form an action/reaction pair.] 25 / 40 A container holds 1 mole of an ideal gas. If the temperature of the gas is held constant and the volume of the gas is halved, the pressure of the gas will double. This happens because the gas particles have gained energy. the gas particles collide with one another more often. the gas particles move more slowly. the gas particles collide with the container walls less often. the gas particles collide with the container walls more often. The correct answer is (E). Pressure is the measure of the rate at which the gas particles collide with the sides of the containers. The more often the gas particles collide with the container walls, the higher the pressure. 26 / 40 Two charged spheres are separated by 2 mm. Which of the following would yield the greatest attractive force? +1q and +4q -1q and -4q +2q and +2q -2q and -2q +2q and -2q The correct answer is (E). The only pair of charged bodies that would attract one another is the pair of unlike charged spheres.The rest of the pairs are like charges, which repel one another. 27 / 40 A stuntman drives a brand new 800kg sports car off a high cliff at 200 km/hour. At the exact moment that the car is driven off the cliff, an 800kg rock is dislodged and falls straight down toward the ground. Which of the following is a correct statement about the event? The car hits the ground first. The rock hits the ground first. The car and the rock hit the ground at the same time. The x velocities of the car and the rock equalize over a period of time. The x accelerations of the car and the rock are different The correct answer is (C). All objects in free fall near the earth are accelerated toward the earth at the same rate. Even though the car is moving along the x-axis at a high rate of speed, as soon as it clears the edge of the cliff it is in free fall. Both the rock and the car start with a y velocity of zero and reach the ground at the same time. 28 / 40 A bat emits a 40 kHz chirp with a wavelength of 8.75 mm toward a tree and receives an echo 0.4 s later. How far is the bat from the tree? 35 m 70 m 105 m 140 m 175 m The speed of the chirp is 29 / 40 A block of mass 3 kg slides down a frictionless inclined plane of length 6 m and height 4 m. If the block is released from rest at the top of the incline, what is its speed at the bottom? 5 m/s 6 m/s 8 m/s 9 m/s 10 m/s First, the kinetic energy the block gains is the same as the potential energy it loses, which is mgh. Since this is equal to mv2, we find that v = . Plugging in g = 10 m/s2 and h = 4 m, we get v = ≈ 9 m/s. 30 / 40 Two spheres are placed into free fall from rest. Sphere B has a mass three times larger than sphere A. Which statement(s) correctly explains the situation? I. Sphere B falls faster. II. Sphere B has more momentum when the two reach the ground. III. Both spheres reach the ground with the same kinetic energy. I only II only I and III only II and II only I, II, and III The correct answer is (B). Both spheres fall from the same height. This means the objects are in free fall, so their accelerations are the same. Sphere B has more mass than sphere A, which gives sphere B more momentum and more kinetic energy when the two spheres reach the ground. 31 / 40 On a cold winter day (5 degrees celsius), the foundation block for a statue is filled with 2.0 m3 of concrete. By how much will the concrete's volume increase on a very warm summer day (35 degrees celsius) if its coefficient of volume expansion is 4.0e-5/ degrees celsius ? 160 cm3 1,200 cm3 1,600 cm3 2,400 cm3 3,200 cm3 The equation for volume expansion is ∆V = delta VVi∆T, so 32 / 40 What information is learned from looking at the curve of an acceleration time graph? The position of the object The displacement of the object The velocity of the object The acceleration of the object None of the above The correct answer is (C). The acceleration-time graph shows a time rate change in velocity. This is the definition of acceleration. 33 / 40 One mole of helium gas and one mole of neon gas are both at STP. Which of the following statements about the gases is correct? Their pressure is the same. Their temperature is the same. Their volume is the same. Their number of particles is the same. The pressure, temperature, volume, and number of particles is the same. The correct answer is (E). At STP the molar volume of any gas is 22.4 L. Standard pressure and volume are also the same for all gases, and of course a mole of any substance is the same number of particles. 34 / 40 A species of hummingbird beats its wings 3,300 times per minute. What frequency of sound will a nearby person hear when the hummingbird flies by? .003 Hz .018 Hz 6 Hz 55 Hz 3300 Hz The correct answer is (D). The frequency at which the humming bird beats its wings is already given in beats per minute. To find the number of wing beats per second (Hz), divide the number of wing beats per minute by 60 seconds. 35 / 40 Two crates are stacked on top of each other on a horizontal floor; crate #1 is on the bottom, and crate #2 is on the top. Both crates have the same mass. Compared with the strength of the force F1 necessary to push only crate #1 at a constant speed across the floor, the strength of the force F2 necessary to push the stack at the same constant speed across the floor is greater than F1 because the force of the floor on crate #1 is greater the coefficient of kinetic friction between crate #1 and the floor is greater the force of kinetic friction, but not the normal force, on crate #1 is greater the coefficient of static friction between crate #1 and the floor is greater the weight of crate #1 is greater With crate #2 on top of crate #1, the force pushing downward on the floor is greater, so the normal force exerted by the floor on crate #1 is greater, which increases the friction force. B, C, D, and E are all false. 36 / 40 A rider on a subway train hears the engineer blow the train whistle. A moment later she hears an answering whistle from an approaching train. Why does the whistle she hears from the approaching train change pitch? The frequency of the waves of the approaching train's whistle is decreasing. The frequency of the waves of the approaching train's whistle is increasing. The loudness of the waves of the approaching train is decreasing. The loudness of the waves of the approaching train is increasing. The echoes of the two trains' whistles are combining. The correct answer is (B). The sound waves from the approaching whistle strike the listener's ears at an increasing rate, producing the increasing pitch. 37 / 40 Redshift of distant galaxies is evidence for which of the following? Expansion of the universe The Uncertainty Principle Black holes Dark matter Superconductivity Redshift occurs when light sources move away from the observer. If all the galaxies in the universe are moving away from us, that's evidence that the universe is expanding. The Uncertainty Principle is a quantum mechanical phenomenon having to do with subatomic particles, not galaxies. The evidence that black holes exist is their gravitational effects on visible objects near them, not redshift. Dark matter has to do with anomalous rotation curves in galaxies, not redshift (though redshift ”specifically, increasing redshift ”is evidence for dark energy). Superconductivity has to do with conducting electricity, not galaxies. 38 / 40 The electron-volt (eV) is a unit of power. voltage. current. potential. energy. The correct answer is (E). The electron carries a negative charge of 1.6e-19C, which is a tiny amount of energy. The electron volt is the energy required to move 1 electron through an electric potential of 1 volt. 39 / 40 A dog walks 120 m due east before turning and running 45 m west. He then turns and trots 40 m due north. After completing his journey, he is 85 m northeast of his home. When he hears his master call him, he runs directly home. Which part of the trip is an equilibrant? The eastward leg The westward leg The northward leg The distance from home The distance to home The correct answer is (E). The resultant vector is the distance the dog is from home. The opposite of the resultant vector is the equilibrant vector. 40 / 40 During a laboratory experiment, a 19.6N pile driver is dropped 2 m on to the head of a nail, which is driven 2.45 cm into a wood board. The frictional force exerted by the wood on the nail is 96.04N 165N 1600N 1960N 3200N The correct answer is (C). This is a work-energy problem. PE = Work → mgh = F·D. Rearrange, substitute, and solve (remember m·g = wt): Your score is The average score is 50% LinkedIn Facebook Twitter VKontakte 0% Restart quiz Previous Quiz Next Quiz