Question 1

Young's modulus is a proportionality constant that relates the force per unit area applied perpendicularly at the surface of an object to:

Accepted Answer

A) the shear 
B) the fractional change in volume 
C) the fractional change in length 
D) the pressure 
E) the spring constant 
A) the shear 
B) the fractional change in volume 
C) the fractional change in length 
D) the pressure 
E) the spring constant

Question 2

The bulk modulus is a proportionality constant that relates the pressure acting on an object to:

Accepted Answer

A) the shear 
B) the fractional change in volume 
C) the fractional change in length 
D) Young's modulus 
E) the spring constant 
A) the shear 
B) the fractional change in volume 
C) the fractional change in length 
D) Young's modulus 
E) the spring constant

Question 3

A force of 5000 N is applied outwardly to each end of a 5.0-m long rod with a radius of 34.0 mm and a Young's modulus of 125   x  108 N/m2.The elongation of the rod is:

Accepted Answer

A) 0.022 mm 
B) 0.0040 mm 
C) 0.11 mm 
D) 0.55 mm 
E) 1.42 mm 
A) 0.022 mm 
B) 0.0040 mm 
C) 0.11 mm 
D) 0.55 mm 
E) 1.42 mm

Question 4

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 5

The diagram shows a stationary 5-kg uniform rod (AC), 1 m long, held against a wall by a rope (AE)and friction between the rod and the wall.To use a single equation to find the force exerted on the rod by the rope at which point should you place the reference point for computing torque?

Accepted Answer

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

Question 6

Which of the following is NOT in equilibrium?

Accepted Answer

A) a rock resting on the ground 
B) a rock sliding at constant velocity across a frictionless surface 
C) a rock rotating in place on a frictionless surface 
D) a rock rotating at a constant rate as it slides at constant velocity across a frictionless surface 
E) a rock falling off a cliff 
A) a rock resting on the ground 
B) a rock sliding at constant velocity across a frictionless surface 
C) a rock rotating in place on a frictionless surface 
D) a rock rotating at a constant rate as it slides at constant velocity across a frictionless surface 
E) a rock falling off a cliff

Question 7

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 8

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 9

A massless meter stick on a horizontal frictionless table top is pivoted at the 80-cm mark.A force   is applied perpendicularly to the end of the stick at 0 cm, as shown.A second force   (not shown)is applied perpendicularly at the 60-cm mark.The forces are in the plane of the table top.If the stick does not move, the force exerted by the pivot on the stick:

Accepted Answer

A) must be zero 
B) must be in the same direction as   and have magnitude
  
C) must be directed opposite to   and have magnitude
  
D) must be in the same direction as   and have magnitude
  
E) must be directed opposite to   and have magnitude
  
A) must be zero 
B) must be in the same direction as   and have magnitude
  
C) must be directed opposite to   and have magnitude
  
D) must be in the same direction as   and have magnitude
  
E) must be directed opposite to   and have magnitude

Question 10

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 11

Two supports, made of the same material and initially of equal length, are 2.0 m apart.A stiff board with a length of 4.0 m and a mass of 10 kg is placed on the supports, with one support at the left end and the other at the midpoint.A block is placed on the board a distance of 0.50 m from left end.As a result the board is horizontal (that is, the downward force on each support is the same).The mass of the block is:

Accepted Answer

A) 0 kg 
B) 2.3 kg 
C) 6.6 kg 
D) 10 kg 
E) 20 kg 
A) 0 kg 
B) 2.3 kg 
C) 6.6 kg 
D) 10 kg 
E) 20 kg

Question 12

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 13

A massless meter stick on a horizontal frictionless table top is pivoted at the 80-cm mark.A force   is applied perpendicularly to the end of the stick at 0 cm, as shown.A second force   (not shown)is applied perpendicularly to the stick at the 100-cm end of the stick.The forces are in the plane of the table top.If the stick does not move, the force exerted by the pivot on the stick:

Accepted Answer

A) must be zero 
B) must be in the same direction as   and have magnitude
  
C) must be directed opposite to   and have magnitude
  
D) must be in the same direction as   and have magnitude
  
E) must be directed opposite to   and have magnitude
  
A) must be zero 
B) must be in the same direction as   and have magnitude
  
C) must be directed opposite to   and have magnitude
  
D) must be in the same direction as   and have magnitude
  
E) must be directed opposite to   and have magnitude

Question 14

The conditions that the sum of forces and the sum of the torques both vanish:

Accepted Answer

A) hold for every solid body in equilibrium 
B) hold only for elastic solid bodies in equilibrium 
C) hold for every solid body 
D) are always sufficient to calculate the forces on a solid object in equilibrium 
E) are sufficient to calculate the forces on a solid object in equilibrium only if the object is elastic 
A) hold for every solid body in equilibrium 
B) hold only for elastic solid bodies in equilibrium 
C) hold for every solid body 
D) are always sufficient to calculate the forces on a solid object in equilibrium 
E) are sufficient to calculate the forces on a solid object in equilibrium only if the object is elastic

Question 15

Three identical uniform rods are each acted on by two or more forces, all perpendicular to the rods.Which of the rods could be in static equilibrium if an additional force is applied at the center of mass of the rod?

Accepted Answer

A) Only 1 
B) Only 2 
C) Only 3 
D) Only 1 and 2 
E) All three 
A) Only 1 
B) Only 2 
C) Only 3 
D) Only 1 and 2 
E) All three

Question 16

A 160-N child sits on a light swing and is pulled back and held with a horizontal force of 100 N.The magnitude of the tension force of each of the two supporting ropes is:

Accepted Answer

A) 60 N 
B) 94 N 
C) 120 N 
D) 190 N 
E) 260 N 
A) 60 N 
B) 94 N 
C) 120 N 
D) 190 N 
E) 260 N

Question 17

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 ball presses against the wall with a force of magnitude:

Accepted Answer

A) 300 N 
B) 350 N 
C) 520 N 
D) 600 N 
E) 690 N 
A) 300 N 
B) 350 N 
C) 520 N 
D) 600 N 
E) 690 N

Exam 12: Equilibrium and Elasticity

Young's modulus is a proportionality constant that relates the force per unit area applied perpendicularly at the surface of an object to:

The bulk modulus is a proportionality constant that relates the pressure acting on an object to:

A force of 5000 N is applied outwardly to each end of a 5.0-m long rod with a radius of 34.0 mm and a Young's modulus of 125 x 108 N/m2.The elongation of the rod is:

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

The diagram shows a stationary 5-kg uniform rod (AC), 1 m long, held against a wall by a rope (AE)and friction between the rod and the wall.To use a single equation to find the force exerted on the rod by the rope at which point should you place the reference point for computing torque?

Which of the following is NOT in equilibrium?

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

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?

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:

The conditions that the sum of forces and the sum of the torques both vanish:

Three identical uniform rods are each acted on by two or more forces, all perpendicular to the rods.Which of the rods could be in static equilibrium if an additional force is applied at the center of mass of the rod?

A 160-N child sits on a light swing and is pulled back and held with a horizontal force of 100 N.The magnitude of the tension force of each of the two supporting ropes is:

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A force of 5000 N is applied outwardly to each end of a 5.0-m long rod with a radius of 34.0 mm and a Young's modulus of 125 x 10⁸ N/m².The elongation of the rod 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 x_com, and the location of the center of gravity x_cog, of the two masses?