University Physics (OpenStax) Vol 1, 2021 P2311 Homework 4 (Ch. 4,5) Assigned: Problems Ch. 4 P 61,62,63,66,69,71, 77 Ch. 5 P 19,20,22,24,25 Concpt.Q. 2 61. 40 m/s^2 62. 215 m/s^2 63. 10.6 rpm 66. (Need R_Earth=6378 km.) v = 7.9 km/s or 7900 m/s 69. a) r=4ti +3tj +5tk m b) r(t)=r'(t) + v_s,s'*t c) v(t)=v'(t) + v_s,s' = v'(t)+(4i+3j+5k) m/s d) a(t) = a'(t) (The two inertial frames of reference, S and S', see the same acceleration.) 71. v_PC = v_PB + v_BC = (2i+3j+4k) + 2j = 2i+5j+4k m/s Ch 5 Conceptual Questions 2. Consider any reference frame that is moving at a constant velocity relative to the Earth's surface to be an "inertial reference frame". (We're assuming that the Earth's surface is not accelerating, which is not true, but at least the acceleration is very low.) a) inertial b) non-inertial c) non-inertial d) non-inertial e) inertial Ch 5 Problems 19. a) Fnet = 5.0i+10.0j N b) Fnet = 11 at 63 degrees 20. a) Fnet = F1 + F2 + F3 = (300-200)i + (500-800)j = 100 i - 300 j N b) magnitude and direction: 316. N at -71.6 degrees 22. F3 = - ( F1 +F2 ) = - ( 225/sqrt(2) i -225/sqrt(2) j ) = - ( 159 i - 159 j) = -159 i + 159 j N 24. Fnet = ma = 63.0kg * 4.200 m/s^2 Fnet = 265 N 25. Find v_f = 12.96 m/s using v_f^2 = 2a(x_f-x_i). Then find time during accel = 3.09 sec. Use t=d/v_avg with vavg=(0+v_f)/2. Or use x = 1/2 at^2 The find time @ constat vel = 6.17 sec. (use t = d/v ) Total time = 9.26 sec Check #62 and #71.