Question 1

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) the sum of the components of all the forces in any direction must equal zero 
D) any two of these forces must be balanced by a third force 
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) the sum of the components of all the forces in any direction must equal zero 
D) any two of these forces must be balanced by a third force 
E) the lines of action of all the forces must pass through the center of gravity of the body

Question 2

A 4.0 m steel beam with a cross sectional area of 1.0 *10-2 m2 and a Young's modulus of 2.0* 1011 N/m2 is wedged horizontally between two vertical walls.In order to wedge the beam, it is compressed by 0.020 mm.If the coefficient of static friction between the beam and the walls is 0.35, the maximum mass (including its own)it can bear without slipping is:

Accepted Answer

A) 0 kg 
B) 36 kg 
C) 70 kg 
D) 360 kg 
E) 700 kg 
A) 0 kg 
B) 36 kg 
C) 70 kg 
D) 360 kg 
E) 700 kg

Question 3

A 5.0 m weightless strut, hinged to a wall, is used to support an 800-N block as shown.The horizontal and vertical components of the force of the hinge on the strut are:

Accepted Answer

A) FH = 800 N, FY = 800 N 
B) FH = 600 N, FY = 800 N 
C) FH = 800 N, FY = 600 N 
D) FH = 1200 N, FY = 800 N 
E) FH = 0 N, FY = 800 N 
A) FH = 800 N, FY = 800 N 
B) FH = 600 N, FY = 800 N 
C) FH = 800 N, FY = 600 N 
D) FH = 1200 N, FY = 800 N 
E) FH = 0 N, FY = 800 N

Question 4

A certain wire stretches 0.90 cm when outward forces with magnitude F are applied to each end.The same forces are applied to a wire of the same material but with three times the diameter and three times the length.The second wire stretches:

Accepted Answer

A) 0.10 cm 
B) 0.30 cm 
C) 0.90 cm 
D) 2.7 cm 
E) 8.1 cm 
A) 0.10 cm 
B) 0.30 cm 
C) 0.90 cm 
D) 2.7 cm 
E) 8.1 cm

Question 5

A ladder leans against a wall.If the ladder is not to slip, which one of the following must be true?

Accepted Answer

A) The coefficient of friction between the ladder and the wall must not be zero 
B) The coefficient of friction between the ladder and the floor must not be zero 
C) Both A and B 
D) Either A or B 
E) Neither A nor B 
A) The coefficient of friction between the ladder and the wall must not be zero 
B) The coefficient of friction between the ladder and the floor must not be zero 
C) Both A and B 
D) Either A or B 
E) Neither A nor B

Question 6

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 7

A net torque applied to a rigid object always tends to produce:

Accepted Answer

A) linear acceleration 
B) rotational equilibrium 
C) angular acceleration 
D) rotational inertia 
E) none of these 
A) linear acceleration 
B) rotational equilibrium 
C) angular acceleration 
D) rotational inertia 
E) none of these

Question 8

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

Question 9

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 10

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 11

A 5.1-kg mass is located at the origin, and a 2.3-kg mass is located at x = 4.9 cm.Assuming g is constant, what is the location of the center of mass xcom, and the location of the center of gravity xcog, of the two masses?

Accepted Answer

A) xcom = 1.5 cm, xcog = 3.4 cm 
B) xcom = 3.4 cm, xcog = 1.5 cm 
C) xcom = 1.5 cm, xcog = 1.5 cm 
D) xcom = 3.4 cm, xcog = 3.4 cm 
E) xcom = 1.5 cm, xcog = 0 cm 
A) xcom = 1.5 cm, xcog = 3.4 cm 
B) xcom = 3.4 cm, xcog = 1.5 cm 
C) xcom = 1.5 cm, xcog = 1.5 cm 
D) xcom = 3.4 cm, xcog = 3.4 cm 
E) xcom = 1.5 cm, xcog = 0 cm

Question 12

To determine if a rigid body is in equilibrium the vector sum of the gravitational forces acting on the particles of the body can be replaced by a single force acting at:

Accepted Answer

A) the center of mass 
B) the geometrical center 
C) the center of gravity 
D) a point on the boundary 
E) none of the above 
A) the center of mass 
B) the geometrical center 
C) the center of gravity 
D) a point on the boundary 
E) none of the above

Question 13

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

Question 14

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 15

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 16

A cube with edges exactly 2 cm long is made of material with a bulk modulus of 3.5 * 109 N/m2.When it is subjected to a pressure of 3.0 * 105 Pa its volume is:

Accepted Answer

A) 7.31 cm3 
B) 7.99931 cm3 
C) 8.00069 cm3 
D) 8.69 cm3 
E) none of these 
A) 7.31 cm3 
B) 7.99931 cm3 
C) 8.00069 cm3 
D) 8.69 cm3 
E) none of these

Question 17

A shearing force of 50 N is applied to an aluminum rod with a length of 10 m, a cross-sectional area of 1.0 *10 - 5 m, and shear modulus of 2.5 *1010 N/m2. As a result the rod is sheared through a distance of:

Accepted Answer

A) zero 
B) 2.0 mm 
C) 2.0 cm 
D) 20 cm 
E) 2.0 m 
A) zero 
B) 2.0 mm 
C) 2.0 cm 
D) 20 cm 
E) 2.0 m

Exam 12: Equilibrium and Elasticity

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

A 5.0 m weightless strut, hinged to a wall, is used to support an 800-N block as shown.The horizontal and vertical components of the force of the hinge on the strut are:

A certain wire stretches 0.90 cm when outward forces with magnitude F are applied to each end.The same forces are applied to a wire of the same material but with three times the diameter and three times the length.The second wire stretches:

A ladder leans against a wall.If the ladder is not to slip, which one of the following must be true?

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 net torque applied to a rigid object always tends to produce:

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:

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

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:

A 5.1-kg mass is located at the origin, and a 2.3-kg mass is located at x = 4.9 cm.Assuming g is constant, what is the location of the center of mass xcom, and the location of the center of gravity xcog, of the two masses?

To determine if a rigid body is in equilibrium the vector sum of the gravitational forces acting on the particles of the body can be replaced by a single force acting at:

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:

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:

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 cube with edges exactly 2 cm long is made of material with a bulk modulus of 3.5 * 109 N/m2.When it is subjected to a pressure of 3.0 * 105 Pa its volume is:

A shearing force of 50 N is applied to an aluminum rod with a length of 10 m, a cross-sectional area of 1.0 *10 - 5 m, and shear modulus of 2.5 *1010 N/m2. As a result the rod is sheared through a distance of:

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A 5.1-kg mass is located at the origin, and a 2.3-kg mass is located at x = 4.9 cm.Assuming g is constant, what is the location of the center of mass x_com, and the location of the center of gravity x_cog, of the two masses?

A cube with edges exactly 2 cm long is made of material with a bulk modulus of 3.5 * 10⁹ N/m².When it is subjected to a pressure of 3.0 * 10⁵ Pa its volume is:

A shearing force of 50 N is applied to an aluminum rod with a length of 10 m, a cross-sectional area of 1.0 10 ^- ⁵ m, and shear modulus of 2.5 10¹⁰N/m².As a result the rod is sheared through a distance of: