Question 1

A horizontal beam of weight W is supported by a hinge and cable as shown.The force exerted on the beam by the hinge has a vertical component that must be:

Accepted Answer

A) nonzero and up 
B) nonzero and down 
C) nonzero but not enough information given to know whether up or down 
D) zero 
E) equal to W 
A) nonzero and up 
B) nonzero and down 
C) nonzero but not enough information given to know whether up or down 
D) zero 
E) equal to W A

Question 2

The uniform rod shown below is held in place by the rope and wall.Suppose you know the weight of the rod and all dimensions.Then you can solve a single equation for the force exerted by the rope, provided you write expressions for the torques about the point:

Accepted Answer

A) 1 
B) 2 
C) 3 
D) 4 
E) 1, 2, or 3 
A) 1 
B) 2 
C) 3 
D) 4 
E) 1, 2, or 3 B

Question 3

A 960-N block is suspended as shown.The beam AB is weightless and is hinged to the wall at A.The tension force of the cable BC has magnitude:

Accepted Answer

A) 720 N 
B) 1200 N 
C) 1280 N 
D) 1600 N 
E) none of these 
A) 720 N 
B) 1200 N 
C) 1280 N 
D) 1600 N 
E) none of these D

Question 4

The 600-N ball shown is suspended on a string AB and rests against the frictionless vertical wall.The string makes an angle of 30 °  with the wall.The line AB goes through the center of the ball, and the contact point with the wall is at the same vertical height as the center of the ball.The magnitude of the tension in the string is:

Accepted Answer

A) 300 N 
B) 520 N 
C) 690 N 
D) 1200 N 
E) none of these 
A) 300 N 
B) 520 N 
C) 690 N 
D) 1200 N 
E) none of these

Question 5

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 (half-way to the plank center).The supporting forces at Y and Z are then:

Accepted Answer

A) FY = 240 N, FZ = 120 N 
B) FY = 200 N, FZ = 40 N 
C) FY = 40 N, FZ = 200 N 
D) FY = 80 N, FZ = 160 N 
E) FY = 160 N, FZ = 80 N 
A) FY = 240 N, FZ = 120 N 
B) FY = 200 N, FZ = 40 N 
C) FY = 40 N, FZ = 200 N 
D) FY = 80 N, FZ = 160 N 
E) FY = 160 N, FZ = 80 N

Question 6

Young's modulus can be correctly given in:

Accepted Answer

A) N.m 
B) N.m2 
C) N.m/s 
D) N/m 
E) joules 
A) N.m 
B) N.m2 
C) N.m/s 
D) N/m 
E) joules

Question 7

The pull P is just sufficient to keep the 14-N block and the weightless pulleys in equilibrium as shown.The tension T in the upper cable is:

Accepted Answer

A) 14 N 
B) 28 N 
C) 16 N 
D) 9.3 N 
E) 19 N 
A) 14 N 
B) 28 N 
C) 16 N 
D) 9.3 N 
E) 19 N

Question 8

For an object in equilibrium the sum of the torques acting on it vanishes only if each torque is calculated about:

Accepted Answer

A) the center of mass 
B) the center of gravity 
C) the geometrical center 
D) the point of application of the force 
E) the same point 
A) the center of mass 
B) the center of gravity 
C) the geometrical center 
D) the point of application of the force 
E) the same point

Question 9

To shear a cube-shaped object, forces of equal magnitude and opposite directions might be applied:

Accepted Answer

A) to opposite faces, perpendicular to the faces 
B) to opposite faces, parallel to the faces 
C) to adjacent faces, perpendicular to the faces 
D) to adjacent faces, neither parallel nor perpendicular to the faces 
E) to a single face, in any direction 
A) to opposite faces, perpendicular to the faces 
B) to opposite faces, parallel to the faces 
C) to adjacent faces, perpendicular to the faces 
D) to adjacent faces, neither parallel nor perpendicular to the faces 
E) to a single face, in any direction

Question 10

A 400-N uniform vertical boom is attached to the ceiling by a hinge, as shown.An 800-N weight W and a horizontal guy wire are attached to the lower end of the boom as indicated.The pulley is massless and frictionless.The tension force T of the horizontal guy wire has magnitude:

Accepted Answer

A) 350 N 
B) 400 N 
C) 690 N 
D) 800 N 
E) 1200 N 
A) 350 N 
B) 400 N 
C) 690 N 
D) 800 N 
E) 1200 N

Question 11

A cylinder placed so it can roll on a horizontal table top, with its center of gravity below its geometrical center, is:

Accepted Answer

A) in stable equilibrium 
B) in unstable equilibrium 
C) in neutral equilibrium 
D) not in equilibrium 
E) none of the above 
A) in stable equilibrium 
B) in unstable equilibrium 
C) in neutral equilibrium 
D) not in equilibrium 
E) none of the above

Question 12

An 80-N uniform plank leans against a frictionless wall as shown.The torque (about point P)applied to the plank by the wall is:

Accepted Answer

A) 40 N.m 
B) 60 N.m 
C) 120 N.m 
D) 160 N.m 
E) 240 N.m 
A) 40 N.m 
B) 60 N.m 
C) 120 N.m 
D) 160 N.m 
E) 240 N.m

Question 13

Young's modulus can be used to calculate the strain for a stress that is:

Accepted Answer

A) just below the ultimate strength 
B) just above the ultimate strength 
C) well below the yield strength 
D) well above the yield strength 
E) none of the above 
A) just below the ultimate strength 
B) just above the ultimate strength 
C) well below the yield strength 
D) well above the yield strength 
E) none of the above

Question 14

A uniform rod AB is 1.2 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, 0.30 m from A.The magnitude of the tension force in the string BD is:

Accepted Answer

A) 8.0 N 
B) 24 N 
C) 32 N 
D) 48 N 
E) 80 N 
A) 8.0 N 
B) 24 N 
C) 32 N 
D) 48 N 
E) 80 N

Question 15

A uniform 240-g meter stick can be balanced by a 240-g weight placed at the 100-cm mark if the fulcrum is placed at the point marked:

Accepted Answer

A) 75 cm 
B) 60 cm 
C) 50 cm 
D) 40 cm 
E) 80 cm 
A) 75 cm 
B) 60 cm 
C) 50 cm 
D) 40 cm 
E) 80 cm

Question 16

The location of which of the following points within an object might depend on the orientation of the object?

Accepted Answer

A) Its center of mass 
B) Its center of gravity 
C) Its geometrical center 
D) Its center of momentum 
E) None of the above 
A) Its center of mass 
B) Its center of gravity 
C) Its geometrical center 
D) Its center of momentum 
E) None of the above

Question 17

A cylinder placed so it can roll on a horizontal table top, with its center of gravity above its geometrical center, is:

Accepted Answer

A) in stable equilibrium 
B) in unstable equilibrium 
C) in neutral equilibrium 
D) not in equilibrium 
E) none of the above 
A) in stable equilibrium 
B) in unstable equilibrium 
C) in neutral equilibrium 
D) not in equilibrium 
E) none of the above

Question 18

A uniform plank is 6.0 m long and weighs 80 N.It is balanced on a sawhorse at its center.An additional 160 N weight is now placed on the left end of the plank.To keep the plank balanced, it must be moved what distance to the right?

Accepted Answer

A) 6.0 m 
B) 2.0 m 
C) 1.5 m 
D) 1.0 m 
E) 0.50 m 
A) 6.0 m 
B) 2.0 m 
C) 1.5 m 
D) 1.0 m 
E) 0.50 m

Question 19

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 pull of the strings on the picture is:

Accepted Answer

A) 2W cos $\theta$ 
B) T sin $\theta$ 
C) T cos $\theta$ 
D) 2T sin$\theta$ 
E) 2T cos$\theta$ 
A) 2W cos $\theta$ 
B) T sin $\theta$ 
C) T cos $\theta$ 
D) 2T sin$\theta$ 
E) 2T cos$\theta$

Question 20

For a body to be equilibrium under the combined action of several forces:

Accepted Answer

A) all the forces must be applied at the same point 
B) all of the forces are composed of pairs of equal and opposite forces 
C) any two of these forces must be balanced by a third force 
D) the sum of the torques about any point must equal zero 
E) the lines of action of all the forces must pass through the center of gravity of the body 
A) all the forces must be applied at the same point 
B) all of the forces are composed of pairs of equal and opposite forces 
C) any two of these forces must be balanced by a third force 
D) the sum of the torques about any point must equal zero 
E) the lines of action of all the forces must pass through the center of gravity of the body

Exam 12: Equilibrium and Elasticity

A horizontal beam of weight W is supported by a hinge and cable as shown.The force exerted on the beam by the hinge has a vertical component that must be:

The uniform rod shown below is held in place by the rope and wall.Suppose you know the weight of the rod and all dimensions.Then you can solve a single equation for the force exerted by the rope, provided you write expressions for the torques about the point:

A 960-N block is suspended as shown.The beam AB is weightless and is hinged to the wall at A.The tension force of the cable BC has magnitude:

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 (half-way to the plank center).The supporting forces at Y and Z are then:

Young's modulus can be correctly given in:

The pull P is just sufficient to keep the 14-N block and the weightless pulleys in equilibrium as shown.The tension T in the upper cable is:

For an object in equilibrium the sum of the torques acting on it vanishes only if each torque is calculated about:

To shear a cube-shaped object, forces of equal magnitude and opposite directions might be applied:

A 400-N uniform vertical boom is attached to the ceiling by a hinge, as shown.An 800-N weight W and a horizontal guy wire are attached to the lower end of the boom as indicated.The pulley is massless and frictionless.The tension force T of the horizontal guy wire has magnitude:

A cylinder placed so it can roll on a horizontal table top, with its center of gravity below its geometrical center, is:

An 80-N uniform plank leans against a frictionless wall as shown.The torque (about point P)applied to the plank by the wall is:

Young's modulus can be used to calculate the strain for a stress that is:

A uniform rod AB is 1.2 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, 0.30 m from A.The magnitude of the tension force in the string BD is:

A uniform 240-g meter stick can be balanced by a 240-g weight placed at the 100-cm mark if the fulcrum is placed at the point marked:

The location of which of the following points within an object might depend on the orientation of the object?

A cylinder placed so it can roll on a horizontal table top, with its center of gravity above its geometrical center, is:

A uniform plank is 6.0 m long and weighs 80 N.It is balanced on a sawhorse at its center.An additional 160 N weight is now placed on the left end of the plank.To keep the plank balanced, it must be moved what distance to the right?

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 pull of the strings on the picture is:

For a body to be equilibrium under the combined action of several forces:

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