Multiple Choice Test For FPSC, PPSC, NTS, CSS
And Various Exams
Subject Physics Chapter # 12 EQUILIBRIUM AND
ELASTICITY
1. A net torque applied to a rigid object always tends to produce:
A. linear acceleration
B. rotational equilibrium
C. angular acceleration
D. rotational inertia
E. none of these
ans: C
2. The conditions that the net force and the net torque both vanish:
A. hold for every rigid 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
ans: A
3. For an object in equilibrium the net torque acting on it vanishes only if each torque is calculated
about:
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
ans: E
4. For a body to be in equilibrium under the combined action of several forces:
A. all the forces must be applied at the same point
B. all of the forces form 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
ans: C
5. For a body to be in equilibrium under the combined action of several forces:
A. all the forces must be applied at the same point
B. all of the forces form 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
ans: D
6. 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. the center of mass
B. the geometrical center
C. the center of gravity
D. a point on the boundary
E. none of the above
ans: C
7. The center of gravity coincides with the center of mass:
A. always
B. never
C. if the center of mass is at the geometrical center of the body
D. if the acceleration due to gravity is uniform over the body
E. if the body has a uniform distribution of mass
ans: D
8. The location of which of the following points within an object might depend on the orientation
of the object?
A. Its center of mass
B. Its center of gravity
C. Its geometrical center
D. Its center of momentum
E. None of the above
ans: B
9. A cylinder placed so it can roll on a horizontal table top, with its center of gravity above its
geometrical center, is:
A. in stable equilibrium
B. in unstable equilibrium
C. in neutral equilibrium
D. not in equilibrium
E. none of the above
ans: B
10. A cylinder placed so it can roll on a horizontal table top, with its center of gravity below its
geometrical center, is:
A. in stable equilibrium
B. in unstable equilibrium
C. in neutral equilibrium
D. not in equilibrium
E. none of the above
ans: A
11. 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 left?
A. 6 . 0m
B. 2 . 0m
C. 1 . 5m
D. 1 . 0m
E. 0 . 50 m
ans: B
12. A window washer attempts to lean a ladder against a frictionless wall. He that the ladder
slips on the ground when it is placed at an angle of less than 75? to the ground but remains in
place when the angle is greater than 75? . The coe?cient of static friction between the ladder
and the ground:
A. is about 0 . 13
B. is about 0 . 27
C. is about 1 . 0
D. depends on the mass of the ladder
E. depends on the length of the ladder
ans: A
13. Stress can be measured in:
A. N/m2
B. N m2
C. N/m
D. N·m
E. none of these (it is unitless)
ans: A
14. Strain can be measured in:
A. N/m2
B. N m2
C. N/m
D. N·m
E. none of these (it is unitless)
ans: E
15. Young’s modulus can be correctly given in:
A. N·m
B. N/m2
C. N·m/s
D. N/m
E. joules
ans: B
16. Young’s modulus is a proportionality constant that relates the force per unit area applied
perpendicularly at the surface of an object to:
A. the shear
B. the fractional change in volume
C. the fractional change in length
D. the pressure
E. the spring constant
ans: C
17. Young’s modulus can be used to calculate the strain for a stress that is:
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
ans: C
18. The ultimate strength of a sample is the stress at which the sample:
A. returns to its original shape when the stress is removed
B. remains underwater
C. breaks
D. bends 180?
E. does none of these
ans: C
19. 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. 0 . 10 cm
B. 0 . 30 cm
C. 0 . 90 cm
D. 2 . 7cm
E. 8 . 1cm
ans: B
20. A force of 5000 N is applied outwardly to each end of a 5 . 0-m long rod with a radius of 34 . 0cm
and a Young’s modulus of 125 × 108 N / m . The elongation of the rod is:
A. 0 . 0020 mm
B. 0 . 0040 mm
C. 0 . 14 mm
D. 0 . 55 mm
E. 1 . 42 mm
ans: D
21. A 4 . 0-m long steel beam with a cross-sectional area of 1 . 0 × 10-2 m2 and a Young’s modulus
of 2 . 0 × 1011 N / m is wedged horizontally between two vertical walls. In order to wedge the beam, it is compressed by 0 . 020 mm. If the coe?cient of static friction between the beam and the walls is 0 . 70 the maximum mass (including its own) it can bear without slipping is:
A. 0
B. 3 . 6kg
C. 36 kg
D. 71 kg
E. 710 kg
ans: E
22. Two supports, made of the same material and initially of equal length, are 2 . 0 m apart. A
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 the left end. As a result the board is horizontal. The mass of the block is:
A. zero
B. 2 . 3kg
C. 6 . 6kg
D. 10 kg
E. 20 kg
ans: E
23. The bulk modulus is a proportionality constant that relates the pressure acting on an object to:
A. the shear
B. the fractional change in volume
C. the fractional change in length
D. Young’s modulus
E. the spring constant
ans: B
24. A cube with edges exactly 2 cm long is made of material with a bulk modulus of 3 . 5×109 N / m
When it is subjected to a pressure of 3 . 0 × 105 Pa its volume is:
A. 7 . 31 cm3
B. 7 . 99931 cm3
C. 8 . 00069 cm3
D. 8 . 69 cm3
E. none of these
ans: B
25. A cube with 2 . 0-cm sides is made of material with a bulk modulus of 4 . 7 × 105 N / m . When
it is subjected to a pressure of 2 . 0 × 105 Pa the length of its any of its sides is:
A. 0 . 85 cm
B. 1 . 15 cm
C. 1 . 66 cm
D. 2 . 0cm
E. none of these
ans: C
26. To shear a cube-shaped object, forces of equal magnitude and opposite directions might be applied:
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 or perpendicular to the faces
E. to a single face, in any direction
ans: B
27. 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 a shear modulus of 2 . 5 × 1010 N / m . As a result the rod is sheared
through a distance of:
A. zero
B. 1 . 9mm
C. 1 . 9cm
D. 19 cm
E. 1 . 9m
ans: B
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