HW4 Fall09 - PHY 317K HOMEWORK # 4 DUE on October 28, 2009...

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PHY 317K HOMEWORK # 4 DUE on October 28, 2009 by 8:00pm Instructions: Use a UT ANSWER SHEET to mark answers. Provide your NAME (last, first), UTEID , and UNIQUE NUMBER of the course. Sign and date it. The answer sheets must be placed in the 317K box located outside PAI 2.48. Late homework will not be graded . Answer the following 67 questions: 1. A uniform plank XY is supported by two equal 120 N forces at X and Y, as shown. The support at X is then moved to Z, which is half-way to the plank's center. (That is, the distance from X to Z is one-fourth the distance from X to Y.) The supporting forces at Y and Z are then: A) F Y = 240 N, F Z = 120 N B) F Y = 200 N, F Z = 40 N C) F Y = 40 N, F Z = 200 N D) F Y = 80 N, F Z = 160 N E) F Y = 160 N, F Z = 80 N 2. Three identical uniform rods are each acted on by two or more forces, all perpendicular to the rods. Which of the rods could be put into static equilibrium if an additional force were applied at the center of mass of the rod? A) Only 1 B) Only 2 C) Only 3 D) Only 1 and 2 E) All three Page 1
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3. A child of weight 145 N sits on a light swing and is pulled back and held with a horizontal force of 72 N. Assuming they are equal, the magnitude of the tension force of each of the two supporting ropes is: A) 58 N B) 74 N C) 81 N D) 94 N E) 110 N 4. A picture P of weight W is hung by two strings as shown. The magnitude of the tension force of each string is T . The total upward force of the strings on the picture is: A) 2 W cos θ B) T sin C) T cos D) 2 T sin E) 2 T cos 5. A man weighing 720 N stands halfway up a 5.0 m ladder of negligible weight. The base of the ladder is 3.0 m from the wall as shown. Assuming that the wall-ladder contact is frictionless, what is the force of the wall on the ladder? (Note: the ladder is stationary, since there is friction at the ladder-floor contact.) A) 160 N B) 210 N C) 270 N D) 350 N E) 410 N Page 2
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6. A uniform rod AB is 1.6 m long and weighs 16 N. It is suspended by strings AC and BD as shown. A block P weighing 96 N is attached at E, 0.40 m from A. The magnitude of the tension force in the string BD is: A) 8.0 N B) 24 N C) 32 N D) 48 N E) 80 N 7. Referring to the same situation as the previous problem, what is the tension in the string AC? A) 60 N B) 70 N C) 80 N D) 90 N E) none of these 8. A 240 N weight is hung from two ropes as shown. The tension in the horizontal rope has magnitude: A) 0 B) 656 N C) 480 N D) 416 N E) 176 N Page 3
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9. A 5.0 m long weightless strut, hinged to a wall, is used to support block weighing 800 N, as shown. The horizontal and vertical components of the force of the hinge on the strut are: A) F H = 800 N, F V = 800 N B) F H = 600 N, F V = 800 N C) F H = 800 N, F V = 600 N D) F H = 1200 N, F V = 800 N E) F H = 0 , F V = 800 N 10. A uniform plank is 4.0 m long and weighs 180 N. The plank is balanced on a sawhorse at its center. An additional 60 N weight is now placed on the left end of the plank. To keep the plank and the extra weight (at the left end of the plank) balanced , they must be
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HW4 Fall09 - PHY 317K HOMEWORK # 4 DUE on October 28, 2009...

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