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.