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.