71. The greatest load which a spring can carry without getting permanently distorted, is called
A. stiffness
B. prof resilience
C. proof stress
D. proof load.

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72. The load on a spring per unit deflection, is called
A. stiffness
B. proof resilience
C. proof stress
D. proof load.

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73. The strain energy stored in a spring when subjected to greatest load without being permanently distorted, is called
A. stiffness
B. proof resilience
C. proof stress
D. proof load.

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74.  A close coil helical spring of mean diameter D consists of n coils of diameter d. If it carries an axial load W, the energy stored in the spring, is
A. 4WD2 n
B. 4W2Dn
C. 44V2D3n
D.4w2D3n2

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75. A close coil helical spring when subjected to a moment M having its axis along the axis of the helix
A. it is subjected to pure bending
B. its mean diameter will decrease
C. its number of coils will increase
D. all the above.

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76. A spring of mean radius 40 mm contains 8 action coils of steel (N = 80000 Nimm2), 4 mm in diameter. The clearance between the coils being 1 mm when unloaded, the minimum compressive load to remove the clearance, is
A. 25 N
B. 30 N
C. 35 N
D. 40 N.

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77.  Flat spiral springs
A. consist of uniform thin strips
B. are supported at outer end
C. are wound by applying a torque
D. all the above.

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