Exam 4 Review Questions PHY 2425 - Exam 4

1 Exam 4H Rev - 1 - Exam 4 Review Questions PHY 2425 - Exam 4 Section: 12 2 Topic: The Center of Gravity Type: Conceptual 8. After a shell explodes at the top of its trajectory, the center of gravity of the fragments has an acceleration, in the absence of air resistance, A) of less than g downward. B) equal to g and downward. C) greater than g and downward. D) of g downward plus a forward component. E) of g downward plus a backward component. Ans: B Section: 12 3 Topic: Some Examples of Static Equilibrium Type: Numerical 12.

2 If you neglect the weight of the boom, what is the maximum weight W that can be suspended from the boom if the horizontal guy wire will break under a tension of kN? A) kN B) kN C) kN D) kN E) kN Ans: E Section: 12 3 Topic: Some Examples of Static Equilibrium Type: Numerical 13. A heavy block is supported by three lines as shown. Which of the following statements is true in its entirety? A) T1 > T2 and T2 > T3 D) T3 > T1 and T1 > T2 B) T2 > T1 and T1 > T3 E) T1 > T3 and T2 > T3 C) T2 > T3 and T3 > T1 Ans: C Exam 4H Rev - 2 - Section: 12 3 Topic: Some Examples of Static Equilibrium Type: Numerical 18.

3 A ball of radius r and mass m is hung using a light string of length L from a frictionless vertical wall. The normal force on the ball due to the wall is rLm A) mgr/L D) mgL/r B) LRLmgr22+ E) None of these is correct. C) LRLmgL22+ Ans: B Section: 12 3 Topic: Some Examples of Static Equilibrium Type: Conceptual 20. A 10-m long plank (of negligible mass) is supported at each end by vertical cables, also of negligible mass. A person of unknown weight sits on the plank between the cables. The tension in the left cable is 300 N, and in the right cable it is 200 N.

4 The person's weight is A) 100 N B) 300 N C) 400 N D) 500 N E) 700 N Ans: D Section: 12 3 Topic: Some Examples of Static Equilibrium Type: Conceptual 21. A 10-m long plank (of negligible mass) is supported at each end by vertical cables. A person of unknown weight sits on the plank between the cables. The tension in the left cable is 300 N, and in the right cable it is 200 N. How far is the person sitting from the left cable? A) m B) m C) m D) m E) m Ans: C Exam 4H Rev - 3 - Section: 12 3 Topic: Some Examples of Static Equilibrium Type: Numerical 22.

5 The sign shown in the figure weighs 200 N. The boom is of uniform construction. If the force exerted by the hinge on the boom is 300 N and acts at an angle of 20 above the horizontal, the tension in the tie cable is A) ~205 N D) ~625 N B) ~145 N E) None of these is correct. C) ~413 N Ans: C Section: 12 3 Topic: Some Examples of Static Equilibrium Type: Numerical 28. The horizontal boom supporting the sign is of uniform construction and weighs 50 N. If the sign weighs 150 N, the force exerted by the hinge on the boom is A) ~350 N D) ~550 N B) ~304 N E) None of these is correct.

6 C) ~25 N Ans: B Section: 12 3 Topic: Some Examples of Static Equilibrium Type: Numerical 31. A ladder is extended to a length of 8 m. It rests against a smooth frictionless vertical wall at an angle of 55 degrees to the horizontal. The ladder has a mass of 30 kg, and its center of mass is three-eighths of the way up the ladder from the floor. If the coefficient of static friction between the ladder and the floor is , calculate how far a man of 80 kg can stand along the ladder without it slipping away at the floor.

7 A) m D) m B) m E) none of the above C) all the way to the top Ans: D Section: 12 7 Topic: Stress and Strain Type: Numerical 48. A wire long has a cross-sectional area of mm2. It is hung vertically, and a mass is hung from it. By how much does the wire stretch if Young's modulus for that material is 1011 N/m2? A) mm B) mm C) mm D) mm E) mm Ans: A Exam 4H Rev - 4 - Section: 12 7 Topic: Stress and Strain Type: Numerical 49.

8 The bulk modulus of water is 109 N/m2. By how much must the pressure be increased to reduce the volume of kg of water from to L? A) 106 N/m2 D) 40 106 N/m2 B) 106 N/m2 E) 106 N/m2 C) 20 106 N/m2 Ans: B Section: 12 7 Topic: Stress and Strain Type: Numerical 52. A wire of circular cross section of diameter d and length L is stretched an amount L by a steady force F. An equal force would produce how much stretch in a similar wire of diameter 2d and length 2L? A) L/8 B) L/4 C) L/2 D) 2 L E) 4 L Ans: C Section: 12 7 Topic: Stress and Strain Type: Numerical 59.

9 An 800-kg mass is hung from a 2-m steel wire with a cross-sectional area of cm2. Young's modulus for steel is 1011 N/m2. How much does the wire stretch? A) mm B) mm C) mm D) mm E) mm Ans: C Section: 12 7 Topic: Stress and Strain Type: Numerical 61. A wire has a diameter of mm. It is stretched of its original length when a mass of 5 kg is hung from it. What is the Young's modulus of the wire? A) 1010 N/m2 D) 108 N/m2 B) 1010 N/m2 E) 108 N/m2 C) 1011 N/m2 Ans: B Section: 12 7 Topic: Stress and Strain Type: Numerical 63.

10 Two wires, A and B, have the same initial length, but the radius of A is four times that of B, and the Young's modulus of A is a third that of B. If the same weight is attached to both wires, what is the ratio of the extension of A divided by the extension of B? A) B) 48 C) D) E) Ans: C Exam 4H Rev - 5 - Section: 13 1 Topic: Density Type: Numerical 3. A piece of wood is floating at the surface of some water as illustrated. The wood has a circular cross section and a height h = cm.