**Helical Spring Experiment Viva Questions and Answers**

**1. What is the principle of a spring?**

Hooke's law

**2. Define Hooke's law.**

According to Hooke's law, within elastic limit, stress is directly proportional to strain.

i.e., Stress/ Strain =a constant

**3. Define strain.**

Strain = Change in dimension /Original dimension

**4. Define stress.**

It is the normal force acting per unit area

Stress = Restoring force/Area

**5. What will you do so that the load attached to the one end of the spring oscillates in the vertical plane in order to obtain simple harmonic oscillations?**

Spring should be suspended vertically and the amplitude of the oscillations should be small.

**6. State the condition under which a spring obeys Hooke's law.**

Extension of the spring should remain within elastic limit.

**7. What are the forces acting on the load that is attached to the spring which is oscillating in a vertical plane?**

The forces are weight and tension.

**8. Define spring constant or force constant of a spring.**

F = -kx; where k is the spring constant. It is the force required to produce unit extension on a spring.

**9. What is the unit of force constant?**

newton / metre (N/m)

**10. What are the conditions essential for the motion of a body to be simple harmonic?**

(a) acceleration is proportional to its distance from the fixed point

(b) acceleration is directed towards a fixed point

**11. What are the factors on which the period of vertical oscillations of a spring depend?**

(a) Directly proportional to the square root of the mass attached

(b) inversely proportional to the spring constant

**12. What is the unit of spring constant?**

Nm^{-1}

**13. Which is more elastic-steel wire or rubber wire of the same diameter and length?**

Steel wire

**14. What is the spring constant in terms of load (M) and extension (e)**

K = Load / Extension = M/e kg/m = (M/e)gNm^{-1}

**15. Aim of Experiment.**

To determine the spring constant by measuring the time period of vertical oscillations of a known load and to check the result by measuring the extension for a known force

**16. Apparatus of Experiment.**

A helical spring, Stand, Slotted weights, Stop-watch etc..

**17. Principle of Experiment.**

i. Vertical oscillations: The period of vertical oscillations of a helical spring is given by,

T = 2π√(M/K)

K = 4π^{2}(M/T^{2})

Where, K = spring constant, M = Total mass attached, T = Period of oscillations

ii. Load extension method: Using Hooke’s law, load is proportional to extension,

Spring constant, K = Load/Extension = mg/l

**18. Procedure of Vertical Oscillations of Experiment**

The given spring is suspended from a rigid support. A weight hanger with a dead load (w_{0}) is suspended at the lower end of the spring (w_{0} should be sufficient to bring the spring in the elastic mood). A pointer is attached to the spring. The weight is slightly pulled down and released. The spring executes vertical oscillations. The time taken for 20 oscillations is noted and the period of oscillation (t/20) is calculated. Changing the loads [say (w_{0}+w), (w_{0}+2w),…..] and the period of oscillations are again determined. In each case M/T_{2} is calculated and hence its mean value is determined. A graph is plotted with M along the X-axis and T_{2} along, the Y-axis. The graph is found to be a straight line. From this K can also be calculated.

**19. Procedure of Load-extension method of Experiment**

The given spring is suspended from a rigid support. A pointer attached to the spring moves over a scale. Reading on the scale for w_{0}, (w_{0}+w), (w_{0}+2w)…. are found. The mean value of scale reading for loading and unloading are r_{0}, r_{1}, r_{2}….. respectively. Extension (l) for loads w, 2w, 3w …. Are given by (r_{1}-r_{0}), (r_{2}-r_{0}), (r_{3}-r_{0}) etc. are calculated. The spring constant,

K = Load/ Extension

A graph is plotted with M along the X-axis and extension along the Y-axis. The graph is found to be a straight line. From this K can also be calculated.