_____ 9. An object is subject to a restoring force of where is the displacement

Question

_____ 9. An object is subject to a restoring force of where is the displacement of the object from its equilibrium position. How much work is done to move the object from to cm? A) 6.22 J B) 0.24 J C) 2.5 x 105 J D) 1.19 x 103 J E) 0.12 J

_____ 11. A 15.0 kg rock is sliding on a rough, horizontal surface at 5.00 m/s and eventually stops due to friction. The coefficient of kinetic friction is 0.210. What average power is produced by friction as the rock stops? A) 154 W B) 147 W C) 31.9 W D) 77.2 W E) 54.5 W

_____ 12. A 1.1 x 103 kg boat at rest moves a distance of 20 m through the water with a forward force of magnitude 3.1 x 103 N. A resistive force due to the water acts on the boat with a force of magnitude 1.8 x 103 N. What is the total work done on the boat? A) 2.6 x 104 J B) 1.3 x 103 J C) 4.9 x 103 J D) 9.8 x 104 J E) 3.2 x 103 J

Explanation / Answer

11. a = - uk g = - 0.210 x 9.8 = - 2.06 m/s^2  

vf = vi + a t

0 =5 - 2.06 t

t = 2.43 sec  

Work done = change in KE = 15(5^2 / 2) = 187.5 J  

P = W / t = 77.2 W

Ans(D)

12. Net force F = (3.1 x 10^3) - (1.8 x 10^3)

F = 1.3 x 10^3 N  

d = 20 m

W = F.d = (1.3 x 10^3) (20)

W = 2.6 x 10^4 J  

Ans(A)

{9 is incomplete question, all data are missing }

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