Physics 6b Winter 2015 Midterm Test Form D Fill out name and perm number on the scantron. Do not forget to bubble in the Test Form (A, B, C, or, D). At the end, only turn in the scantron. Keep questions/cheat sheets, etc. You may want to keep a record of your answers to double- check the scantron results. (Solutions will be provided). Do not turn this page until you have been instructed to do so
1 1) Two identical small charged spheres are a certain distance apart, and each one initially experiences an electrostatic force of magnitude F due to the other. With time, charge gradually leaks off of both spheres. When each of the spheres has lost half its initial charge, the magnitude of the electrostatic force will be A) 1/4 F. B) 1/8 F. C) 1/16 F. D) 1/2 F. 2) A mass M is attached to an ideal massless spring. When this system is set in motion with amplitude A, it has a period T. What is the period if the amplitude of the motion is increased to 2A? A) T/2 B) 2T C) 2T D) T E) 4T 3) A cup of water containing an ice cube at 0 C is filled to the brim. The tip of the ice cube sticks out of the surface. As the ice melts, you observe that A) the water level remains the same. B) the cup might overflow but it depends on the actual mass of the ice cube. C) the water level actually goes down. D) the cup overflows. E) There is not enough information to answer this question. 4) Consider a pipe of length L that is open at both ends. What are the wavelengths of the three lowest-pitch tones produced by this pipe? A) 4L, 2L, L B) 2L, L, L/2 C) 2L, L, L/2 D) 2L, L, 2L/3 E) 4L, 4L/3, 4L/5 5) A certain frictionless simple pendulum having a length L and mass M swings with period T. If both L and M are doubled, what is the new period? A) T B) 2T C) 2T D) 4T E) T/4 6) A certain coin has a diameter of 21.21 mm, a thickness of 1.95 mm, and weighs 0.04905 N. What is its density? A) 29.1 10 3 kg/m 3 B) 9.25 10 3 kg/m 3 C) 71.2 10 3 kg/m 3 D) 2.31 10 3 kg/m 3 E) 7.26 10 3 kg/m 3
7) X and Y are two uncharged metal spheres on insulating stands, and are in contact with each other. A positively charged rod R is brought close to X as shown in Figure (a). 2 Sphere Y is now moved away from X, as in Figure (b). What are the final charge states of X and Y? A) Both X and Y are negative. B) X is positive and Y is neutral. C) X is negative and Y is positive. D) Both X and Y are neutral. E) X is neutral and Y is positive. 8) A rock is under water in a shallow lake. As the rock sinks deeper and deeper into water, the buoyant force on it A) remains constant. B) increases. C) decreases. 9) A guitar string is fixed at both ends. If you tighten it to increase its tension A) the frequencies of its vibrational modes will increase but its wavelengths will not be affected. B) the wavelength increases but the frequency is not affected. C) both the frequency and the wavelength increase. 10) An object is attached to a vertical ideal massless spring and bobs up and down between the two extreme points A and B. When the kinetic energy of the object is a minimum, the object is located A) 1/ 2 times the distance from A to B. B) 1/3 of the distance from A to B. C) 1/4 of the distance from A to B. D) midway between A and B. E) at either A or B.
11) A frictionless pendulum clock on the surface of the earth has a period of 1.00 s. On a distant planet, the length of the pendulum must be shortened slightly to have a period of 1.00 s. What is true about the acceleration due to gravity on the distant planet? A) The gravitational acceleration on the planet is equal to g. B) We cannot tell because we do not know the mass of the pendulum. C) The gravitational acceleration on the planet is slightly less than g. D) The gravitational acceleration on the planet is slightly greater than g. 3 12) The figure shows two unequal point charges, q and Q, of opposite sign. Charge Q has greater magnitude than charge q. In which of the regions X, Y, Z will there be a point at which the net electric field due to these two charges is zero? A) only region Y B) only region Z C) only region X D) only regions X and Z E) all three regions 13) In the figure Q = 5.8 nc and all other quantities are accurate to 2 significant figures. What is the magnitude of the force on the charge Q? (k = 1/4!" 0 = 8.99 10 9 N m 2 /C 2 ) A) 9.0 10-4 N B) 1.0 10-3 N C) 1.2 10-3 N D) 1.8 10-3 N 14) A simple harmonic oscillator has an amplitude of 3.50 cm and a maximum speed of 26.0 cm/s. What is its speed when the displacement is 1.75 cm? A) 17.0 cm/s B) 22.5 cm/s C) 15.0 cm/s D) 12.0 cm/s E) 14.2 cm/s 15) A standing wave is oscillating at 690 Hz on a string, as shown in the figure. What is the speed of traveling waves on this string? A) 280 m/s B) 210 m/s C) 140 m/s D) 410 m/s
16) Two people are talking at a distance of 3.0 m from where you are and you measure the sound intensity as 1.1 10-7 W/m 2. Another student is 4.0 m away from the talkers. What sound intensity does the other student measure? Assume that the sound spreads out uniformly and undergoes no significant reflections or absorption. A) 8.3 10-8 W/m 2 B) 2.5 10-8 W/m 2 C) 6.2 10-8 W/m 2 D) 7.8 10-7 W/m 2 E) 1.5 10-7 W/m 2 4 17) The weight of a car of mass 1.20 10 3 kg is supported equally by the four tires, which are inflated to the same gauge pressure. What gauge pressure in the tires is required so the area of contact of each tire with the road is 1.00 10 2 cm 2? (1 atm = 1.01 10 5 Pa.) A) 2.94 10 4 Pa B) 11.6 10 4 Pa C) 2.94 10 3 Pa D) 11.6 10 5 Pa E) 2.94 10 5 Pa 18) The density of aluminum is 2700 kg/m 3. If transverse waves propagate at 34 m/s in a 4.6-mm diameter aluminum wire, what is the tension on the wire? A) 31 N B) 62 N C) 42 N D) 52 N 19) Water flows through a pipe having a varying width. More water flows per second through the wide section than through the narrow section because there is more room for it to flow. A) True B) False 20) A positive point charge Q is fixed on a very large horizontal frictionless tabletop. A second positive point charge q is released from rest near the stationary charge and is free to move. Which statement best describes the motion of q after it is released? A) As it moves farther and farther from Q, its acceleration will keep increasing. B) Its speed will be greatest just after it is released. C) As it moves farther and farther from Q, its speed will keep increasing. D) As it moves farther and farther from Q, its speed will decrease. E) Its acceleration is zero just after it is released.
21) Four traveling waves are described by the following equations, where all quantities are measured in SI units and y represents the displacement. I: y = 0.12 cos(3x - 21t) II: y = 0.15 sin(6x + 42t) III: y = 0.13 cos(6x + 21t) IV: y = -0.27 sin(3x - 42t) Which of these waves have the same period? A) I and II, and also III and IV B) I and IV, and also II and III C) I and III, and also II and IV D) All of them have the same period. E) They all have different periods. 5 22) A point charge Q is located a short distance from a point charge 3Q, and no other charges are present. If the electrical force on Q is F, what is the electrical force on 3Q? A) F B) 3F C) 3F D) F/ 3 E) F/3 23) An object of mass 8.0 kg is attached to an ideal massless spring and allowed to hang in the Earth's gravitational field. The spring stretches 3.6 cm before it reaches its equilibrium position. If this system is allowed to oscillate, what will be its frequency? A) 2.1 Hz B) 2.6 Hz C) 0.67 Hz D) 0.0045 Hz 24) In simple harmonic motion, the speed is greatest at that point in the cycle when A) the kinetic energy is a minimum. B) the displacement is a maximum. C) the magnitude of the acceleration is a maximum. D) the magnitude of the acceleration is a minimum. E) the potential energy is a maximum. 25) A 1.0-C point charge is 15 m from a second point charge, and the electric force on one of them due to the other is 1.0 N. What is the magnitude of the second charge? (k = 1/4!" 0 = 8.99 10 9 N m 2 /C 2 ) A) 25 C B) 0.025 C C) 25 nc D) 10 nc E) 1.0 C
Answer Key Testname: MIDTERM-D 1) A 2) D 3) A 4) D 5) B 6) E 7) C 8) A 9) A 10) E 11) C 12) C 13) D 14) B 15) A 16) C 17) E 18) D 19) B 20) C 21) C 22) A 23) B 24) D 25) C