Spring MCQs – Part 1

Practice SSC JE and other civil engineering exam questions on springs: close-coiled and open-coiled helical springs under axial load and axial torque, stiffness, springs in series and parallel, proof load, proof resilience, flat spiral springs and where the maximum shear stress occurs in the wire. Tap an option to check it, then open the full explanation for each question.

Question 1Easy

Pick the correct statement from the following:

Full explanation

Answer: D. All options are correct

All three are standard definitions, so (d).

Question 2Medium

A close-coiled helical spring absorbs 30 N·mm of energy while extending by 5 mm. Its stiffness will be:

Full explanation

Answer: A. 2.4 N/mm

U = ½kδ² → 30 = ½k(25) → k = 2.4 N/mm. (Book key (c) 6 N/mm divides energy by extension.)

Question 3Easy

The predominant effect of an axial tensile force on a (close-coiled) helical spring is:

Full explanation

Answer: D. Twisting

The axial load acts at a lever arm R from the wire centre, so each section carries a torque WR — the wire is twisted.

Question 4Easy

The equivalent stiffness of two springs of stiffness S₁ and S₂ joined in series is:

Full explanation

Answer: A. S₁S₂/(S₁ + S₂)

Series: same force, deflections add → 1/S = 1/S₁ + 1/S₂ → S = S₁S₂/(S₁ + S₂).

Question 5Easy

Flat spiral springs are used in:

Full explanation

Answer: D. watches

A flat spiral (clock) spring stores energy when wound and releases it slowly as torque — used in watches and clocks.

Question 6Medium

An open-coiled helical spring of mean diameter D, number of coils N and wire diameter d is subjected to an axial force P. The wire of the spring will be subjected to:

Full explanation

Answer: C. combined shear, bending and twisting

With a large helix angle α, the moment PR splits into a torque PR cos α and a bending moment PR sin α, plus direct shear.

Question 7Medium

A close-coiled helical spring is subjected to a torque about its axis. The spring wire would experience:

Full explanation

Answer: A. bending stress

An axial couple T acts about the spring axis, which is perpendicular to the wire axis in a close coil — so each wire section carries a bending moment M = T.

Question 8Medium

The angle of twist (wind-up) of a close-coiled helical spring under an axial torque T is given by (D = mean coil diameter, d = wire diameter, n = number of coils):

Full explanation

Answer: B. 64TDn/(Ed⁴)

Wire is in uniform bending M = T over length L = πDn: θ = TL/(EI) = T·πDn/(E·πd⁴/64) = 64TDn/(Ed⁴).

Question 9Easy

The load on a spring per unit deflection is called:

Full explanation

Answer: A. stiffness

k = W/δ — the stiffness (spring rate).

Question 10Easy

The greatest load which a spring can carry without getting permanently distorted is called:

Full explanation

Answer: D. proof load

That limiting load is the proof load.

Question 11Easy

The strain energy stored in a spring when subjected to the greatest load without being permanently distorted is called:

Full explanation

Answer: B. proof resilience

Energy at the proof load = proof resilience = ½ Wproof δ.

Question 12Medium

The maximum shear stress occurs on the outermost fibres of a circular shaft under torsion. In a close-coiled helical spring, the maximum shear stress occurs on the:

Full explanation

Answer: C. innermost fibres

At the inner side of the coil, torsional and direct shear add, and coil curvature raises the stress further.