22 Created by Master Student Physics Practice Test #5 1 / 40 Scientists identify the elements that are burning in the stars by using which of the following devices? Refractive telescopes Reflective telescopes Spectroscopes Polarimeters Photoelectric microscopes The correct answer is (C). Scientists look at the light from a star by passing the light through a spectometer, which separates the starlight into the individual line spectra of the elements that are burning in the star. 2 / 40 A traveling wave has a frequency of 6.0 Hz, an amplitude of 0.2 m, and a wavelength of 0.5 m. What is its wave speed? 0.1 m/s 0.6 m/s 1.2 m/s 2.4 m/s 3.0 m/s Use the equation that relates wavelength, frequency, and wave speed. 3 / 40 During practice, an athlete runs in a straight line from point X to point Y, and then back along the same path from Y to X. If she runs at a constant speed of 3 m/s from X to Y, and then at a constant speed of 6 m/s from Y to X, what is her average speed for the entire run? 3.5 m/s 4 m/s 4.5 m/s 5 m/s 5.5 m/s Perhaps the easiest way answer this question is to choose a numerical value for the distance between X and Y. Let's choose 180 m. Then the time it takes the athlete to run from X to Y is 60 seconds, and the time it takes to run from Y back to X is 30 seconds. Her average speed for the entire run is the total distance traveled, 180 m + 180 m = 360 m, divided by the total time, 60 s + 30 s = 90 s. This gives an average speed for the entire trip of (360 m)/(90 s) = 4 m/s. (Note: You would get the same answer, 4 m/s, no matter what positive value you chose for the distance between X and Y.) 4 / 40 When a net force acts upon an object, the object is at rest. gaining mass. losing mass. accelerating. moving at constant velocity. The correct answer is (D). A net force applied to a body causes the body to be accelerated. This is Sir Isaac Newton's second law of motion, F = ma. 5 / 40 An electric circuit is composed of a pair of parallel 30 ohm resistors in series with a 9 ohm resistor. The current through the 9 ohm resistor is .25 A.What is the voltage applied to the circuit? 1.5 V 3 V 6 V 12 V 24 V The correct answer is (C). To solve the problem you must first find the equivalent resistance of the two parallel resistors. The resistors are the same value; so divide 30 ohms by 2, which gives a value of 15 ohms. Add 15 ohms to the 9 ohms in series with the parallel resistors for a total resistance of 24 ohms. The voltage is equal to the current multiplied by the resistance, Ohm's Law. (24ohm)(.25) = 6 V. 6 / 40 The binding energy of a nucleus is equal to the average energy of each nucleon. the energy needed to split the nucleus into its parts. the mass-energy difference between protons and neutrons. the energy necessary to overcome the neutron-neutron repulsion. the energy required to remove a proton from the nucleu The correct answer is (B). The binding energy is the result of the conversion of the mass defect into the energy that holds the protons in the nucleus in spite of their repulsion for each other. 7 / 40 A pendulum swings at a rate of .75 vibrations/second. The frequency of the vibrations would decrease because ¦ Mass of the bob was increased Length of the pendulum was increased Mass of the bob was decreased Length of the pendulum was decreased Displacement from zero was increased The correct answer is (B). The frequency is the inverse of the period. Lengthening the pendulum increases the length of the period, which means the frequency decreases. 8 / 40 The engineer of a train blows the train whistle as he approaches a crossing. A few moments later he hears an echo from the whistle. The engineer hears the echo of the whistle because of reflection. refraction. constructive interference. destructive interference. Doppler effect. The correct answer is (A). An echo is the repeat sound heard when the original sound waves strike a fixed object and return toward their origin. This is the process of reflection. 9 / 40 A force is applied to an object that is free to move.Which of the following statements is correct? The frictional force is larger than the applied force. The frictional force is smaller than the applied force. The weight of the object is larger than the applied force The weight of the object is smaller than the applied force All of these statements could be correct. The correct answer is (E). Without more information about the applied force, all of the choices could be correct. 10 / 40 An Imperial battle cruiser, sitting in a hanger deck, is measured to have a length of 200 m by a worker on the deck. If the cruiser travels at a speed of c past a planet, what will be the length of the cruiser, as measured by the inhabitants of the planet? Between 0 and 200 m 200 m Greater than 200 m None of the above, since it is impossible to reach the described speed Special relativity dictates that length contracts for objects moving at relativistic speeds, so the length should be smaller. That's C. (Bear in mind that the speed is attainable because the square root of three is less than 2, so the speed is less than the speed of light.) Mathematically, you could calculate the length as follows. If v = ()c, then the relativistic factor is 11 / 40 When Johannes Kepler developed his laws for the movement of planetary bodies, one of the laws stated that the orbits of the planets about the sun are circular. elliptical. parabolic. sinusoidal. straight lines. The correct answer is (B). One of Kepler's observations in his laws of planetary motion was that the planets orbit the sun in elliptical orbits. 12 / 40 A box with a mass of 2 kg accelerates in a straight line from 4 m/s to 8 m/s due to the application of a force whose duration is 0.5 s. Find the average strength of this force. 2 N 4 N 8 N 12 N 16 N The impulse delivered to the ball, J = ∆t, equals its change in momentum. Thus, 13 / 40 The symbols used in writing nuclear equations. Atomic nuclei are typically written in the form . Which letter represents the atomic number? The number of protons is Z. The number of neutrons is X. The symbol of the element is X. The number of electrons is A. The mass number is A. The correct answer is (A). The number of protons and the atomic number are the same quantity. The Z number represents the atomic number. 14 / 40 New thermos bottles have the ability to keep hot substances hot for several days. The thermos bottles have a highly polished interior made of stainless steel, which makes them almost unbreakable. These thermos bottles keep substances hot by reducing heat loss due to absorption conduction convection radiation evaporation The correct answer is (D). The highly polished interior surface of the thermos bottle reflects radiated heat from the substance back into the substance it is keeping hot. 15 / 40 A flat plane is raised until a block resting on its surface just slides down the plane at a constant rate. Which statement(s) is/are true? I. The parallel force equals the frictional force. II. The weight of the object equals the frictional force. III. The perpendicular force equals the normal force. I only II only I and III only II and III only I, II, and III The correct answer is (A). The force down the plane is a component of the weight of the block, which is found by multiplying the weight of the object by the sine θ of the angle to which the plane is raised. This produces a force down the plane, which will accelerate the object when the plane is raised high enough. The frictional force between the block and the plane always acts against the motion of the object-in this case, friction operates up the plane. Since there is no acceleration, the frictional force (Ff) opposing the motion of the block exactly equals the downward force (F11). 16 / 40 If the pressure acting on an ideal gas that is kept at constant temperature is multiplied by four, its volume triples. reduces to 1/3. increases by four. reduces to 1/4. There is not enough information to tell. The correct answer is (D). An ideal gas follows Boyle's law. If the pressure increases by a factor of four, the volume decreases by a factor of four. Whatever the change in one, the other is indirectly related by the same factor. 17 / 40 Due to the magnetic force, a positively charged particle undergoes uniform circular motion in a uniform magnetic field. Which of the following changes could cause the radius of the circular path to decrease? Increase the mass of the particle Increase the speed of the particle Decrease the charge of the particle Decrease the strength of the magnetic field None of the above The magnetic force provides the centripetal force on the charged particle. It follows that 18 / 40 An object is moving in a circular path with a constant velocity (v). If the radius of the circle in which the object is moving is decreased by one half and the velocity remains the same, what will happen to the centripetal force? It will be 4F. It will be 2F. It will be F. It will be F/2. It will be F/4. The correct answer is (B). Since the centripetal force is found with the equation Fc = (m)(v2)/r we can change the r value to .5r and substitute it into the equation and solve to find the relative force. Fc = (m)(v2)/.5r. Clearly the force will be double when the radius is halved and the velocity remains the same. 19 / 40 A 6 volt battery is connected across a resistor, and a current of 1.5 A flows in the resistor. What is the value of the resistor? 2ohm 4ohm 6ohm 8ohm 10ohm The correct answer is (B). This is a problem that requires an Ohm's Law calculation to find resistance. Rearrange the equation to find resistance. 20 / 40 Compare a bucket of boiling water to a cup of boiling water. Which statement(s) can be made about the two containers? I. The heat content of the two is the same. II. The temperature of the two is the same. III. The bucket of water contains more heat and is therefore hotter I only II only I and III only II and III only I, II, and III only The correct answer is (B). The heat content of a substance is dependent on three different things, the specific heat of the substance, the mass of the substance, and the temperature of the substance. The specific heat can be disregarded since the substance is the same for both containers. The mass of the water in the cup is less than the mass of the water in the bucket, therefore the cup of water has less heat content than the bucket of water even though they are at the same temperature. 21 / 40 In which type of decay is the identity of the nucleus unchanged? Electron capture Gamma decay Alpha decay alpha decay delta V+ decay A nucleus in an excited energy state can relax to a lower energy state by releasing energy. If the photon(s) emitted in this process are in the gamma-ray portion of the electromagnetic spectrum, we refer to this decay as gamma decay. The numbers of protons and neutrons remain unchanged. 22 / 40 If a container contains a mixture of two ideal gases (of different molecular masses) at thermal equilibrium, which of the following is true? The average kinetic energy of the molecules of the lighter gas is less than the average kinetic energy of the molecules of the heavier gas. The average kinetic energy of the molecules of the lighter gas is greater than the average kinetic energy of the molecules of the heavier gas. The average speed of the molecules of the lighter gas is less than the average speed of the molecules of the heavier gas. The average speed of the molecules of the lighter gas is equal to the average speed of the molecules of the heavier gas. The average speed of the molecules of the lighter gas is greater than the average speed of the molecules of the heavier gas. Since the gases are in thermal equilibrium in the same container, they're at the same temperature, and because the average kinetic energy of the molecules is proportional to the temperature, the fact that their temperatures are the same implies that the average kinetic energy of their molecules is the same also. This eliminates A and B. Now, in order for the lighter molecules to have the same average kinetic energy as the heavier ones, the lighter molecules must be moving faster on average, so E is correct. 23 / 40 An astronaut visits the planet Mars, which has less of a gravitational acceleration than the earth. While on Mars, the astronaut will notice that his weight is less and his mass is greater. weight is the same and his mass is the same. weight is less and his mass is the same. weight is the same and his mass is less. weight is less and his mass is less. The correct answer is (C). The weight of the astronaut is dependent upon the gravitational attraction of the planetary body. Mars has a lower gravitational attraction than the earth, so the astronaut weighs less on Mars. The mass of an object, or a person, is an intrinsic quality of a body that does not change. 24 / 40 A person who weighs 800 N steps onto a scale that is on the floor of an elevator car. If the elevator accelerates upward at a rate of 5 m/s2, what will the scale read? 400 N 800 N 1000 N 1200 N 1600 N First draw a free-body diagram. 25 / 40 A white disk and a black disk are placed on top of a snow bank on a sunny day. The black disk sinks deeper into the snow because the black disk reflects light better. the white disk reflects light better. the black disk radiates heat better. the white disk radiates heat better. both of the disks reflect light and radiate heat at the same rate. The correct answer is (C). The black disk absorbs heat better than the white disk, and it radiates heat away faster. 26 / 40 The mean distance from Saturn to the sun is 9 times greater than the mean distance from Earth to the sun. How long is a Saturn year? 18 Earth years 27 Earth years 81 Earth years 243 Earth years 729 Earth years Kepler's Third Law says that T2 ∠R3 for a planet with a circular orbit of radius R. Since T ∠, if R increases by a factor of 9, then T increases by a factor of 27 / 40 Which one of the following statements is true concerning the motion of an ideal projectile launched at an angle of 45 degrees to the horizontal? The acceleration vector points opposite to the velocity vector on the way up and in the same direction as the velocity vector on the way down. The speed at the top of the trajectory is zero. The object's total speed remains constant during the entire flight. The horizontal speed decreases on the way up and increases on the way down. The vertical speed decreases on the way up apeed changes. D is false because the horizontal component is constant throughout the motion. Since the acceleration of the projectile is always downward (because it's gravitational acceleration), the vertical speed decreases as the projectile rises and increases as the projectile falls. A is false because the acceleration vector is straight down, but the velocity is never straight up or straight down. It would be true of the vertical component of the velocity, but not of the total velocity. B is false because the projectile still has its horizontal velocity at the top of the trajectory. C is false because the vertical component of the velocity changes, even if the horizontal component does not, so the total speed changes. D is false because the horizontal component is constant throughout the motion. 28 / 40 An astronaut lives on a spaceship that is moving at a speed of c away from the earth. As measured by a clock on the spaceship, the time interval between her maintenance checks on the ship's main computer is 15 months. In the reference frame of the team here on Earth that monitors the ship's progress, what is the time interval between maintenance checks on the ship's main computer? Always less than 15 months Always exactly 15 months Always more than 15 months Initially less than 15 months, but after time more than 15 months Initially more than 15 months, but after time less than 15 months Special relativity says that time dilates for objects moving at relativistic speeds, so the time should be greater (and never change). You could compute the exact value of the time as follows. If v = c, then the relativistic factor is 29 / 40 Which of the following is true concerning a bi-concave lens? Its focal length is positive. It cannot form real images. It cannot form virtual images. It can magnify objects. None of the above A bi-concave lens is a diverging lens. Diverging lenses (like convex mirrors) have negative focal lengths and therefore cannot form real images. (Notice that D is false; diverging lenses and convex mirrors always form diminished, virtual images, as you can verify using the mirror and magnification equations.) 30 / 40 Which type of decay would cause the atomic number of the nucleus to increase? Alpha decay alpha decay delta V+ decay Electron capture Gamma decay When a nucleus undergoes alpha decay, a neutron is converted into a proton and an electron, and the electron is ejected. Because of this, the number of protons in the nucleus ”the atomic number ”is increased by 1. 31 / 40 Which of the following best describes the condition of an enclosed gas during an isothermal expansion? The gas remains at constant pressure. The gas remains at constant volume. The gas remains at constant temperature. The gas remains at constant density. The gas remains at constant molarity. The correct answer is (C). An isothermal process is a process in which the temperature of the system remains constant. 32 / 40 For an ohmic conductor, doubling the voltage without changing the resistance will cause the current to decrease by a factor of 4 decrease by a factor of 2 remain unchanged increase by a factor of 2 increase by a factor of 4 The equation I = implies that increasing V by a factor of 2 will cause I to increase by a factor of 2. 33 / 40 A paperboy rides his bicycle down the street and throws the papers to houses as he rides by them. When a thrown paper leaves his hand, which of the following statements is NOT true about the paper? Its velocity changes. Its acceleration changes. Its displacement changes. Its position relative to the earth changes. Its position relative to the paperboy changes. The correct answer is (B). Once the paperboy releases the paper from his hand, the paper is in free fall. All objects in free fall near the earth experience the same constant acceleration. 34 / 40 When a voltage source that is inducing voltage into a large number of coils is disconnected, and a switch that is in series with the coils of wire is also opened, a spark is observed to jump across the switch terminals as the switch begins to open up. What is the cause of this spark? Free electrons from the voltage source Free electrons from the coils of wire Collapse of the magnetic field in the coils of wire Secondary electron flow from the source Stored voltage in the coils of wire The correct answer is (C). When the voltage is disconnected there is a small lag time between the disconnection of the current and the ceasing of the flow because the magnetic field, which is induced into the wires, collapses. This produces a current flow that causes the spark. 35 / 40 What is the de Broglie wavelength of a proton whose linear momentum has a magnitude of 3.3e-23 kg * m/s ? 0.0002 nm 0.002 nm 0.02 nm 0.2 nm 2 nm The de Broglie wavelength of a particle whose momentum is p is λ= h/p. For this proton, we find that 36 / 40 A rescue plane flying at 162 km/hr drops a survival package to a group of stranded skiers from a height of 70 m. After dropping the package the pilot of the plane continues to fly in a straight line. When the package strikes the ground it is 85 m behind the plane. 170 m behind the plane. 255 m behind the plane. 462 m behind the plane. directly beneath the plane. The correct answer is (E). This is a curvilinear problem. The package already has the x-axis (horizontal) velocity of the plane. Even though the package accelerates toward the ground, its horizontal velocity remains exactly the same as when it left the plane, and that keeps the package moving along under the airplane until it strikes the ground. 37 / 40 A spring accelerates a 2 kg cart from rest in a time of .8 seconds, giving it a momentum of 4 kg·m/s. With what force did the spring accelerate the cart? .5N 1.6N 3.2N 5N 8N The correct answer is (D). The impulse impressed onto the cart is the same as the momentum the cart achieves. The momentum is given as P = mv, which was given to the cart in a time of .8 sec. The impulse an object receives in a given time is Ft = (delta)P. The solution is found by replacing the P (momentum), yielding the equation Ft = mv, which is rearranged to find the force. F = (m)(v)/t. 38 / 40 A hanging weight stretches a spring 8 cm. If the weight is doubled and the spring constant is not exceeded, how much will the spring stretch? 4 cm 8 cm 12 cm 16 cm 20 cm The correct answer is (D). Based on Hooke's Law, F = kx where F is mg and x is the elongation. Solving for x = mg/k, so if m is doubled, x is doubled as well. 39 / 40 The most notable difference between a radio wave and a light wave is speed. refractive index. reflectivity. amplitude. frequency. The correct answer is (E). Both light and radio waves are electromagnetic radiation. The difference between the two is their frequency. 40 / 40 A thrown baseball hits and breaks a glass window and ends up inside the house. Which of the following is correct about the ball? The force the ball exerted on the window was larger than the force the window exerted on the ball. The force the ball exerted on the window was smaller than the force the window exerted on the ball. The force the ball exerted on the window was the same as the force the window exerted on the ball. Since the ball broke the window, it didn't lose any momentum. The kinetic energy the ball had before it broke the window equaled the kinetic energy the ball had after it broke the window. The correct answer is (C). All forces occur in pairs, are equal in magnitude and oppositely directed. The pairs of forces are the ball on the window, and the window on the ball, which are equal and opposite. Your score is The average score is 47% LinkedIn Facebook Twitter VKontakte 0% Restart quiz Previous Quiz Next Quiz