# PHYSICS 151

##### University of Hawaii, Manoa Dept. of Physics & Astronomy

Instructor: Michael Nassir
Office: Watanabe Hall, Rm. 426, (808) 956-2922
E-mail: nassir @ hawaii.edu

## ANSWERS to FINAL EXAM from SPRING 2006

Entirely Multiple-Choice (on bubble sheet):

unit conversions:
1.
D  3.8x10^14 micrometers
2. E  9100 kPa
3. C  22,400 cm^3
4. A  3.3x10^-7 kg*m^2

5. B  sqrt(2)  (K = (1/2)mv^2)

6. E  85 kJ  (W = mgh)
7. D  430 W  (P=W/t)
8. E  4.0 m/s  (use conservation of momentum)
9. B  inelastic  (40 J of kinetic energy is lost in collision)
10. A  (net torque = I * ang.accel.)
11. C  (either center-of-mass at 50-cm position OR net torque about pivot = 0)

12. A  0.0027 m/s^2  (g = GM/r^2)
13. C  (a_rad = v^2/r;  ang.veloc. = constant, so ang.accel. = 0)
14. D  (period does not depend on mass of [small] satellite)
15. E  (I = MR^2;  T^2 = (4pi^2/GM)*r^3;  L=mvr & v^2=GM/r)

16. E  589 N  (normal force = mg + ma, and a=0)
17. E  829 N  (normal force = mg + ma, and a=4)
18. C  349 N  (normal force = mg + ma, and a=-4)
19. D  12 m/s  ( v(8s) = v(5s) + a*(t since 5s) )
20. A  0 m/s
21. B  18 m  ( y(8s) = y(5s) + v(5s)*(t since 5s) + (1/2)*a*(t since 5s) )

22. D  (Newton's 3rd Law: both F and impulse are equal & opposite. Newton's 2nd Law: a = F/m --- masses unequal, so accelerations unequal)
23. E  (use conservation of momentum)
24. A  (use conservation of energy: kinetic is converted to elastic-potential)
25. A  (formula for period of mass-on-spring)
26. A  (F = ma and F = -kx)

27. B  29 N  (vector addition - triangle method is fast in this case)
28. D  51 N
29. A  3.6 m/s  (use trig to find monkey starts at height of 0.670, then use conservation of energy)
30. C  4.5 s  (use formula for period of pendulum)
31. D  (tension = weight + centripetal force = mg + mv^2/r)
32. C  (vines must hold more weight, therefore have greater tensions)
33. B  (conservation of energy in #29 shows: v at bottom depends only on starting height, NOT on mass)
34. B  (period of pendulum in #30 does NOT depend on mass of pendulum bob)
35. B  (use conservation of energy)
36. B  (amplitude diminishes as energy is lost;  period of pendulum in #30 does NOT depend on amplitude of swings)

37. C  1 L of water is heaviest  (all four weights are: 1N, 0.981N, 9.81N, and 0.981N)
38. C  (object floats if its density is less than density of fluid)
39. D  3.52 km  (at depth h, P = density*g*h)
40. T  5.32x10^8 N  (F = P*A)
41. D  Doppler Effect
42. B  Beats
43. A  Archimedes's Principle
44. C  Bernoulli's Principle

45. E  14 m  (wavelength = v / f)
46. E  75 m/s  (wavelength of fundamental = 2L  & v = wavelength * f)
47. E  125 Hz  (4th overtone = 5th harmonic;  f_5 = 5 * f_1)
48. D  (speed depends on tension, and frequency depends on speed;  wavelength depends only on L)
49. B  (transverse waves have amplitude of wave's displacement perpendicular to direction of wave travel)
50. C
51. E  773 Hz  (wavelength = (4/3)*L  &  f = v / wavelength)

52. D  4.186 kJ  (100 mL is 100 g of water;  Q = m*c*(delta T) )
53. A  (solid = left-hand region, liquid = upper-right region, vapor = lower-right region)
54. B  (no -- at 75K, substance is vapor below 0.5 atm)
55. B  (at 2 atm, boiling point is approx. 340 K)
56. E  490 degC  (P1/T1 = P2/T2, and convert temps to kelvins)
57. A  (W = P*(delta V), and here V does not change)
58. A  ( (delta U) = Q - W;  #57 says that W=0, and question says that heat Q is added, so (delta U) > 0 )
59. B  (adiabatic means that Q=0, but question says that heat Q is added)
60. A  29.2%  (e = (Q_H - Q_L) / Q_H)
61. C  328 degC  (e = (T_H - T_L) / T_H, and convert temps to kelvins)