# Practice Final

## Physics 140 with Evrard at University of Michigan - Ann Arbor *

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#### Related Textbooks:

University Physics with Modern Physics with MasteringPhysics (12th Edition)
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1. A coin lies on a wooden plank a distance 2 m from its right edge. The plank is slowly raised with the coin remaining stationary. When the coin is 1.2 m above the ground, it begins to slide along the plank. What is the value of the coefficient of static friction between the plank and the coin? a)0.80 b)0.75 c)0.60 d)0.40 e)0.25 2. (P) The diagrams below show identical masses held by strings under tension. The pulleys are frictionless and the same type of string is used in each case. Consider the longest string segment in case 2. Rank the cases according to the wave speed in the string, largest to smallest? a)1, 3, 2 b)3, 2, 1 c)2, 1, 3 d)1=3 (tie), 2 e)1, 2=3 (tie) 3. A damped harmonic oscillator consists of a block of mass 2.5 kg attached to a spring with spring constant 10 N/m to which is applied a damping force (in Newtons) of the form F= -0.1v, with v the velocity in m/s. The spring is stretched a distance x m and released. After four complete oscillations, what fraction of the mechanical energy is retained by the system? a)0.99 b)0.90 c)0.77 d)0.60 e)0.48 4. Chocolate milk is pumped through a vertical section of pipe shown below. Compared to the lower level (location 1), the milk flow at the upper level (2) a)has greater speed and lower pressure. b)has greater speed and greater pressure. c)has lower speed and lower pressure. d)has lower speed and greater pressure. e)has the same speed and lower pressure. 5. (P) Which of the following items cannot be associated with simple harmonic motion? a)The amplitude of motion is small. b)The acceleration varies with time in a sinusoidal manner. c)The mechanical energy of the system is not constant. d)The direction of the force is opposite that of the displacement. e)The magnitude of the force increases as the square of the displacement. 6. In the left figure below (case i), mass m makes small oscillations on a spring with period T. In the right figure (case ii), the spring has been cut in half and the same mass is then attached. What is the period of small oscillations for the system in case (ii)? (Hint: Consider the long spring to be two short springs in series.) a) 2T b) √2 T c) T / 2 d) T / √2 e) T 7. (P) Mr. Snowy, the snow figure shown below, slides down a frictionless incline angled θ degrees (0<θ<π/2) above horizontal. Which statement(s) listed below about the Mr. Snowy system are correct? a)The acceleration along the incline depends on the mass of Mr. Snowy. b)The contact force between the lower and middle balls of Mr. Snowy has non-zero components parallel and perpendicular to the direction of the incline. c)The speed of Mr. Snowy increases with time in a linear fashion. d)both b) and c) e)all of a), b) and c) 8. (P) A water main enters a house 2.0 m below ground level. A small diameter pipe carries water to a second-story faucet located 5.0 m above ground level. When the faucet is opened (and no other outlets of water are in use in the house), water of density 1000 kg/m 3 flows at 1.3 m/s in the main line and 3.0 m/s at the faucet. What is the pressure difference between the faucet and the main line when water is flowing? a)-4.3 x 10 4 Pa b)-6.5 x 10 4 Pa c)-7.2 x 10 4 Pa d)-9.2 x 10 4 Pa e)-1.4 x 10 5 Pa θ 9. (P) A solid object has weight 15.46 N when weighed by a spring scale in air. When entirely submerged in salt water of density 1030 kg/m 3 , the spring scale reads 5.46 N. What is the density of the object? a)1510 kg/m 3 b)1530 kg/m 3 c)1550 kg/m 3 d)1570 kg/m 3 e)1590 kg/m 3 10. A metal hoop starts from rest and rolls down an inclined plane without slipping. Which of the following statements about the hoop’s motion is false? a)There is no static friction force at the contact point of the hoop with the incline. b)The kinetic energy of the hoop has rotational and translational components. c)Positive work is done by gravity as the hoop rolls down the incline. d)Measured about its center, the torque on the hoop is non-zero. e)The top of the hoop moves with twice the speed of its center of mass. 11. A planet of radius R has an interior consisting of a dense core of constant mass density ρ and radial extent R/2 surrounded by a mantle of lower mass density ρ/3. Which of the following curves represents the magnitude of the gravitational force as a function of distance from the center of the planet? A B C D a)A b)B c)C d)D e)none of the above 12. An irate driver sounds the horn of his horn while accelerating steadily from rest away from an intersection of two straight roads. An audio recorder hidden in the center of the intersection records the horn’s fundamental frequency to shift from 500 Hz at t=0 (when the car just passes over the recorder) to 475 Hz at t=4.5 s. What is the acceleration of the car? (Use a speed of sound of 343 m/s.) a)2.2 m/s 2 b)3.5 m/s 2 c)4.0 m/s 2 d)4.9 m/s 2 e)5.8 m/s 2 13. (P) The diagram below represents a snapshot of a standing wave on a string taken at a moment when the displacement is at a maximum. The string is 1.22 m long and has mass 6.64 g and is under a tension of 11 N. What is the period of oscillation of the string? a)9.0 ms b)8.2 ms c)6.6 ms d)4.5 ms e)3.0 ms 14. An ice cream truck initially traveling at 24 m/s hits the brakes. For the truck to stop over a distance of 35 m, what magnitude of (constant) deceleration is required of the brakes? a)3.3 m/s 2 b)5.6 m/s 2 c)8.2 m/s 2 d)10.1 m/s 2 e)13.3 m/s 2 15. Ball A, with mass m and velocity v, makes a head-on, elastic collision with stationary ball B of mass 2m . After the collision, what are the velocities (v A , v B ) of the pair? a)-v/3, 2v/3 b)-v, 2v c)v/3, -2v/3 d)-2v/3, v/3 e)0, v/2 16. A block (#1 below) of mass 0.2 kg slides along the upper frictionless surface shown below at an initial speed of 8 m/s. It undergoes an inelastic collision with another block (#2) that is attached at the equilibrium position of a spring with spring constant 1200 N/m. An impulsive collision occurs (the spring does not affect the collision outcome) and afterwards block #2 is observed to oscillate with a period of 0.14s. Block #1 slides off the upper surface, falling through a vertical distance h=4.9m. What is the horizontal distance d? a)4.0 m b)4.4 m c)4.8 m d)5.2 m e)5.6 m 17. The figure below represents the pressure variation observed at the origin (x=0) for a sound wave traveling in a dense gaseous medium with speed of sound 250 m/s. Using x in meters and t in seconds, which equation represents this pressure wave? a)Δp(x,t) = (8 mPa) sin(2πx - 2000πt) b)Δp(x,t) = (8 mPa) sin(2πx + 1000πt) c)Δp(x,t) = (8 mPa) sin(4πx + 2000πt) d)Δp(x,t) = (8 mPa) sin(4πx - 1000πt) e)Δp(x,t) = (16 mPa) sin(2πx - 1000πt) 18. Dumbbells, consisting of equal mass balls attached by stiff, light rods, lie on horizontal, frictionless ice. The same impulsive force F is applied over a brief interval Δt to each dumbbell in different ways, shown as (a) and (b) below. After the impulses are applied, how do the kinetic energies of the dumbbells in the two cases compare? a)K a =K b b)K a =2K b c)K a =K b /2 d)K a =4K b e)K a =K b /4 19. In the U-tubes below, light and dark areas show liquids of different densities. In which situation(s) is it impossible for the liquids to be in static equilibrium? a)1 b)2 c)3 d)4 e)both 2 and 3 20. (P) Two identical blocks of mass m=0.25 kg are connected by a massless string over a frictionless pulley of radius R=0.1 m. The coefficient of kinetic friction between the block and table is µ k =0.2 and the pulley has rotational inertia I=0.01 kg m 2 . If the string does not slip on the pulley, what is the magnitude of its angular acceleration? a)39.2 rad/s 2 b)31.5 rad/s 2 c)25.4 rad/s 2 d)18.6 rad/s 2 e)13.1 rad/s 2 21. A bat navigates by sending and receiving sonar waves as it flies. Imagine that the bat emits sonar at a fixed frequency. Under what situations will the frequency of the sonar received by the bat be higher than the frequency emitted? a)The bat is flying parallel to the walls of a deep canyon. b)The bat is diving toward the ground. c)The bat is flying east at 8 m/s behind a crow also heading east at 10 m/s. d)both a) and b) e)all of a), b) and c) 22. At your last physics lecture, you witness a farewell egg toss involving a wren’s egg (W) and a zebra woodpecker’s egg (Z). The trajectories for eggs W and Z are shown below. Which egg had the larger initial horizontal velocity? a)W b)Z c)both have the same initial horizontal velocity d)need more information e)no more egg problems - yeah! Z W Answer Key V2 # 1.b 5 2.d/a7 3.d 9 4.a 10 5.e/c3 6.d 11 7.d/b|c8 8.c 4 9.e/c13 10.a 1 11.c 2 12.c 15 13.a/d16 14.c 6 15.a 17 16.a 12 17.d 19 18.c 18 19.e/b|c14 20.e/a20 21.b 20 22.b 20

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