Question 1

A 3-m long wire with a diameter of 1.5 mm has a Young's modulus of 9 $\times$ 1010 N/m2.What mass hung from the wire would extend it by 3 mm?

Accepted Answer

A) 159 kg 
B) 5.20 kg 
C) 16.2 kg 
D) 64.8 kg 
E) None of the above 
A) 159 kg 
B) 5.20 kg 
C) 16.2 kg 
D) 64.8 kg 
E) None of the above

Question 2

The boom in the figure is uniform and weighs 2.20 kN.The magnitude of the tension in the guy wire is

Accepted Answer

A) ~0.635 kN 
B) ~1.83 kN 
C) ~1.94 kN 
D) ~1.47 kN 
E) None of these is correct. 
A) ~0.635 kN 
B) ~1.83 kN 
C) ~1.94 kN 
D) ~1.47 kN 
E) None of these is correct.

Question 3

A wire 2.5-m long has a cross-sectional area of 2.5 mm2.It is hung vertically,and a 4.5-kg mass is hung from it.By how much does the wire stretch if Young's modulus for that material is 2.0 $\times$ 1011 N/m2?

Accepted Answer

A) 0.22 mm 
B) 2.2 mm 
C) 0.022 mm 
D) 0.72 mm 
E) 0.072 mm 
A) 0.22 mm 
B) 2.2 mm 
C) 0.022 mm 
D) 0.72 mm 
E) 0.072 mm

Question 4

The horizontal bar in the figure will remain horizontal if

Accepted Answer

A) L1 = L2 and R1 = R2  
B) L1 = L2 and M1 = M2  
C) R1 = R2 and M1 = M2  
D) L1M1 = L2M2  
E) R1L1 = R2L2  
A) L1 = L2 and R1 = R2  
B) L1 = L2 and M1 = M2  
C) R1 = R2 and M1 = M2  
D) L1M1 = L2M2  
E) R1L1 = R2L2

Question 5

A body is in translational equilibrium when

Accepted Answer

A) it is acted on by a constant force. 
B) no friction forces are involved. 
C) it has a constant acceleration. 
D) it has a constant velocity. 
E) no contact forces are involved. 
A) it is acted on by a constant force. 
B) no friction forces are involved. 
C) it has a constant acceleration. 
D) it has a constant velocity. 
E) no contact forces are involved.

Question 6

The bulk modulus B has units of

Accepted Answer

A) force. 
B) energy. 
C) pressure. 
D) mass per unit time. 
E) mass density. 
A) force. 
B) energy. 
C) pressure. 
D) mass per unit time. 
E) mass density.

Question 7

If you measure the force required to stretch a typical laboratory spring as a function of the amount of stretch,which of the graphs shown below would best represent your data?

Accepted Answer

A) 1 
B) 2 
C) 3 
D) 4 
E) 5 
A) 1 
B) 2 
C) 3 
D) 4 
E) 5

Question 8

A wire has a diameter of 0.75 mm.It is stretched 0.2% of its original length when a mass of 5 kg is hung from it.What is the Young's modulus of the wire?

Accepted Answer

A) 1.4 $\times$ 1010 N/m2  
B) 5.6 $\times$ 1010 N/m2  
C) 1.7 $\times$ 1011 N/m2  
D) 5.6 $\times$ 108 N/m2  
E) 1.4 $\times$ 108 N/m2  
A) 1.4 $\times$ 1010 N/m2  
B) 5.6 $\times$ 1010 N/m2  
C) 1.7 $\times$ 1011 N/m2  
D) 5.6 $\times$ 108 N/m2  
E) 1.4 $\times$ 108 N/m2

Question 9

Use the figure to the right to answer the next problem.
A ball of mass m and radius r is placed next to a step of height ½ r.  
-What is the force F needed to just lift the ball off the floor?

Accepted Answer

A) 0.5 mg 
B) 1.41 mg 
C) 1.73 mg 
D) mg 
E) None of these is correct. 
A) 0.5 mg 
B) 1.41 mg 
C) 1.73 mg 
D) mg 
E) None of these is correct.

Question 10

A body is in mechanical equilibrium when

Accepted Answer

A) it is moving with constant acceleration. 
B) it is being moved by a constant force. 
C) the sum of the external forces acting on it is zero. 
D) the sum of the external torques acting on it is zero. 
E) it is moving with constant velocity. 
A) it is moving with constant acceleration. 
B) it is being moved by a constant force. 
C) the sum of the external forces acting on it is zero. 
D) the sum of the external torques acting on it is zero. 
E) it is moving with constant velocity.

Question 11

Use the following to answer the question:  
-The point that identifies the fracture point of the material whose graph of stress as a function of strain is shown below is

Accepted Answer

A) 1 
B) 2 
C) 3 
D) 4 
E) 5 
A) 1 
B) 2 
C) 3 
D) 4 
E) 5

Question 12

Use the following to answer the question:  
-The horizontal boom supporting the sign is of uniform construction and weighs 50 N.If the sign weighs 150 N,the tension in the supporting cable is

Accepted Answer

A) ~350 N 
B) ~303 N 
C) ~25 N 
D) ~550 N 
E) None of these is correct. 
A) ~350 N 
B) ~303 N 
C) ~25 N 
D) ~550 N 
E) None of these is correct.

Question 13

The force combination that forms a simple couple is

Accepted Answer

A)    and   
B)    and   
C)    and   
D)    and   
E)    and   
A)    and   
B)    and   
C)    and   
D)    and   
E)    and

Question 14

A wire of circular cross section of diameter d and length L is stretched an amount $\Delta$L by a steady force F.An equal force would produce how much stretch in a similar wire of diameter 2d and length 2L?

Accepted Answer

A) $\Delta$L/8 
B) $\Delta$L/4 
C) $\Delta$L/2 
D) 2$\Delta$L 
E) 4$\Delta$L 
A) $\Delta$L/8 
B) $\Delta$L/4 
C) $\Delta$L/2 
D) 2$\Delta$L 
E) 4$\Delta$L

Question 15

The magnitude of the resultant couple acting on the rectangular plate is

Accepted Answer

A) 160 N·m 
B) 45 N·m 
C) 115 N·m 
D) 205 N·m 
E) None of these is correct. 
A) 160 N·m 
B) 45 N·m 
C) 115 N·m 
D) 205 N·m 
E) None of these is correct.

Question 16

An upright refrigerator tips over if its

Accepted Answer

A) height is greater than its width. 
B) center of mass is below its middle. 
C) center of mass is above its middle. 
D) center of mass is at its middle. 
E) center of mass projects onto the floor at a point outside the outline of its base. 
A) height is greater than its width. 
B) center of mass is below its middle. 
C) center of mass is above its middle. 
D) center of mass is at its middle. 
E) center of mass projects onto the floor at a point outside the outline of its base.

Question 17

Use the picture on the right to answer the next question. A steel wire and an aluminum wire of the same length L and diameter d are joined to form a wire of length 2L.The wire is fastened to the ceiling and a mass m is attached to the other end.  
-The strain in the aluminum portion is ____ the steel portion.

Accepted Answer

A) less than 
B) equal to 
C) greater than 
D) depends on how tight m is attached to the steel 
E) unable to tell 
A) less than 
B) equal to 
C) greater than 
D) depends on how tight m is attached to the steel 
E) unable to tell

Question 18

A flat object resting on a horizontal frictionless surface is acted on by forces of equal magnitude as shown.The center of gravity of the object is indicated in each case.The object is in translational equilibrium in figure(s)

Accepted Answer

A) 3 and 4 
B) 1 and 2 
C) 2 and 4 
D) 1 only 
E) 4 only 
A) 3 and 4 
B) 1 and 2 
C) 2 and 4 
D) 1 only 
E) 4 only

Exam 12: Static Equilibrium and Elasticity

A 3-m long wire with a diameter of 1.5 mm has a Young's modulus of 9 ×\times× 1010 N/m2.What mass hung from the wire would extend it by 3 mm?

The boom in the figure is uniform and weighs 2.20 kN.The magnitude of the tension in the guy wire is

A wire 2.5-m long has a cross-sectional area of 2.5 mm2.It is hung vertically,and a 4.5-kg mass is hung from it.By how much does the wire stretch if Young's modulus for that material is 2.0 ×\times× 1011 N/m2?

The horizontal bar in the figure will remain horizontal if

A body is in translational equilibrium when

The bulk modulus B has units of

If you measure the force required to stretch a typical laboratory spring as a function of the amount of stretch,which of the graphs shown below would best represent your data?

A wire has a diameter of 0.75 mm.It is stretched 0.2% of its original length when a mass of 5 kg is hung from it.What is the Young's modulus of the wire?

Use the figure to the right to answer the next problem. A ball of mass m and radius r is placed next to a step of height ½ r. -What is the force F needed to just lift the ball off the floor?

A body is in mechanical equilibrium when

Use the following to answer the question: -The point that identifies the fracture point of the material whose graph of stress as a function of strain is shown below is

Use the following to answer the question: -The horizontal boom supporting the sign is of uniform construction and weighs 50 N.If the sign weighs 150 N,the tension in the supporting cable is

The force combination that forms a simple couple is

A wire of circular cross section of diameter d and length L is stretched an amount Δ\DeltaΔ L by a steady force F.An equal force would produce how much stretch in a similar wire of diameter 2d and length 2L?

The magnitude of the resultant couple acting on the rectangular plate is

An upright refrigerator tips over if its

A flat object resting on a horizontal frictionless surface is acted on by forces of equal magnitude as shown.The center of gravity of the object is indicated in each case.The object is in translational equilibrium in figure(s)

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A 3-m long wire with a diameter of 1.5 mm has a Young's modulus of 9 $\times$ 10¹⁰N/m².What mass hung from the wire would extend it by 3 mm?

A wire 2.5-m long has a cross-sectional area of 2.5 mm².It is hung vertically,and a 4.5-kg mass is hung from it.By how much does the wire stretch if Young's modulus for that material is 2.0 $\times$ 10¹¹ N/m²?

A wire of circular cross section of diameter d and length L is stretched an amount $\Delta$ L by a steady force F.An equal force would produce how much stretch in a similar wire of diameter 2d and length 2L?