Dept. of Physics & Astronomy

Office: Watanabe Hall, Rm. 426, (808) 956-2922

E-mail: nassir @ hawaii.edu

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PHYS 151 Exam & Answers page*

**Entirely Multiple-Choice (on bubble sheet):**

unit conversions:**
1. **D 6.6x10^-4 GW

**5.** A "a" only (graph of constant v = horizontal graph, slope = 0)

**6.** E "a, b, & f" (constant accel -> graph with constant slope = straight line)

**7.** C "e & f" (negative accel -> graph with negative slope at all times)

**8.** D "e & f" (slowing down -> graph getting closer to zero at all times)

**9.** C 17.1 m/s (v_0 = sqrt(2*g*h_peak) )

**10.** A 1.7 s (t = v_0 / g)

**11.** D momentum of cannonballer (p = m*v; since v decreases over time, p also decreases)

**12.** C 700 N (F = (coeff of friction)*m*g)

**13.** B 0.35 (coeff of friction = F / (m*g) )

**14.** B 1.9 kJ (Work = F * d)

**15.** D 803 N (F_drag = weight = m*g)

**16.** D constant momentum (p = m*v, and v = constant)

**17.** C 2.0 m (want center-of-mass position at point where suspension cable attaches = 1.5 m)

**18.** D point D (E_tot is conserved, so K is largest when U=m*g*y is smallest)

**19.** B equal to v_A (E_tot is conserved; since U_C=U_A, we see that K_C=K_A, so v_C=v_A)

**20.** A 20. m (E_B = E_D, so (K + U)_B = (K + U)_D, and use U_B=m*g*y to find y_B)

**21.** B equal to (E_tot is conserved)

**22.** E cannot determine using only the information given (conserv of E gives us v^2_A - v^2_E, but NOT v_A - v_E!)

**23.** C greater than (friction causes (K + U) to decrease over time)

**24.** E 2.8 m/s (impulse = delta(p) = p_f - p_i; use p_f = m*v_f to find v_f)

**25.** B 75 N (F = impulse / t)

**26.** B equal in strength (Newton's 3rd Law: force of paddle on puck = equal & opposite to force of puck on paddle)

**27.** B 1/3 (T = 2*pi / omega)

**28.** B 1/3 (L is conserved, so I_init * omega_init = I_final * omega_final )

**29.** C (L is conserved/constant, but K_rot = (1/2)*I*omega^2 becomes 3x larger)

**30.** D 1.7 rad/s^2 (alpha = delta(omega) / t)

**31.** B 13 rev (use rotational kinematics to find: delta(theta) = 84.0 rad, then convert rad -> revolutions)

**32.** A 190 kg/m^3 (density = m/V, where m = 14*75kg, and V = 5500 L = 5.5 m^3 )

**33.** A yes (object floats if: density(object) < density(fluid); here: 190 kg/m^3 < 1000 kg/m^3)

**34.** D 97 atm (P = F/A, where F = m*g, and convert final answer from [Pa] to [atm])

**35.** A roof will bulge upward/outward (Bernoulli's Principle: as v increases, P decreases)

**36.** E 20. kcal (Q = m*c*delta(T), where delta(T) = 37degC - 10degC = 27degC = 27K)

**37.** B heat of vaporization ("vaporization"=boiling -- NOT needed here; "fusion"=melting)

**38.** A entropy increases (delta(S) = Q/T, where Q = heat of fusion and T=273K, so delta(S) is positive)

**39.** D 30. m (wavelength = 2*L for fundamental mode)

**40.** A wire A has higher-frequency fundamental (wire A has lower (m/L), so wire A has faster v, and both wires have same wavelength)

**41.** B transverse waves (displacement of wire is perpendicular to direction of wave propagation)

**42.** E 60. m/s (v = wavelength * frequency)

**43.** D 10. Hz (frequency of nth overtone = n*f_1 = 2 Hz, 4 Hz, 6 Hz, 8 Hz, 10 Hz, ...)

**44.** E 7.0 m (period of ideal pendulum: T = 2*pi*sqrt(L/g) )

**45.** B period is unchanged (formula for T does NOT depend on mass of pendulum bob)

**46.** C 1 (period: T = 2*pi*sqrt(m/k) -- does NOT depend on amplitude of oscillations)

**47.** B 1/4 (E_tot = (1/2)*k*A^2, so when A=d, energy is 1/4 as large as when A=2d )

**48.** A 1/2 (v_max = A*sqrt(k/m), so when A=d, v_max is 1/2 as large as when A=2d )

**49.** D 7.2 cm (Hooke's Law: F_spring = k*x)

**50.** A 0.92 Hz (resonance occurs when f_driving = f_natural = sqrt(k/m) / (2*pi) )

**51.** C amplitude grows larger (description of resonant growth)

**52.** D isothermal (constant temperature)

**53.** A adiabatic (no heat added/removed)

**54.** B isobaric (constant pressure)

**55.** C Newton's 3rd Law of Motion

**56.** A Newton's 1st Law of Motion

**57.** E Kepler's 3rd Law

**58.** D Newton's Law of Universal Gravitation

**59.** C Doppler Effect

**60.** D Pascal's Principle

**61.** A Archimedes' Principle

**62.** E Principle of Superposition (of waves)

**63.** E Energy, Momentum, and Angular Momentum (three major conserved quantities & Conservation Laws)