30. Im Figure P5 30, the man and the platform together 33. A 72.0-ky mom stands on a spring scoke in on eley- weigh 950 N. The pulley com be modeled o friction- stor. Starting from meat the elevator ascends, othering less. Determine how hard the mun bus to pull on the its meximom speed of 1.20 mk in 0 800 s. It travels rope to lift himself steadily upwound above the ground. with this constant speed for the next 5.00 s. The clay- (Or is it impossible? If so, explain why ) shor them undergoes a uniform acceleration in the meg ative y direction for 1 50 s and comes to rest. What does the spring scule register (8) before the elevator stores to move, (b) during the first 0.600 s, (c) while the elevator is traveling at constant speed, and (d) dur- ing the time interval it is slowing down? 34. To the Atwood machine shown in Figure 5 14g, m = 200 king and m. = 7.00 ka. The masses of the pul- ley and string are negligible by comparison The pul- le turns without friction and the string does not stretch. The lighter object is released with a sharp push that sets it into motion ot v = 2.40 ms downward. (@) Figure PS.30 How for will m, descend below its inkid level? (bj Find the velocity of m ofter 1.80 seconds 31. In the system shown in Figure P5.31, a horizontal force E, exces on the 6.00-ing object. The horizontal Section 5.8 Forces of Friction surface is frictionless. Consider the acceleration of the sliding object as a function of F. (@) For what values of F. does the 2.00-ky object accelerate upward? (b) For what values of F is the tension in the cord zero? (c) Plot the acceleration of the 6 00-ky object versus F.. Include value of F. from -100 Nto +100 N