JEE Challenger
More from Oscillations

Frequency of Oscillation for Cut Spring Mass System

The frequency of oscillation of a mass mm suspended by a spring is ν1\nu_1. If the length of the spring is cut to half, the same mass oscillates with frequency ν2\nu_2. The value of ν2ν1\frac{\nu_2}{\nu_1} is _________.

Options

A

11

B

22

C

2\sqrt{2}

Correct
D

3\sqrt{3}

Topics & Concepts

OscillationsSHM

Step-by-Step Solution

To find the ratio of the frequencies of oscillation, we analyze how the spring constant depends on the length of the spring.

The frequency of oscillation ν\nu of a mass mm attached to a spring with spring constant kk is given by: ν=12πkm\nu = \frac{1}{2\pi} \sqrt{\frac{k}{m}}

For a given spring material and cross-section, the spring constant kk is inversely proportional to its original length LL: k1L    kL=constantk \propto \frac{1}{L} \implies k \cdot L = \text{constant}

Let the initial length of the spring be L1=LL_1 = L and its spring constant be k1k_1. The initial frequency of oscillation is: ν1=12πk1m\nu_1 = \frac{1}{2\pi} \sqrt{\frac{k_1}{m}}

When the spring is cut to half of its original length, its new length becomes L2=L2L_2 = \frac{L}{2}. Using the inverse proportionality relation: k2L2=k1L1k_2 L_2 = k_1 L_1 k2(L2)=k1L    k2=2k1k_2 \left(\frac{L}{2}\right) = k_1 L \implies k_2 = 2k_1

The new frequency of oscillation ν2\nu_2 with the same mass mm is: ν2=12πk2m=12π2k1m\nu_2 = \frac{1}{2\pi} \sqrt{\frac{k_2}{m}} = \frac{1}{2\pi} \sqrt{\frac{2k_1}{m}}

Taking the ratio of the two frequencies: ν2ν1=12π2k1m12πk1m=2k1k1=2\frac{\nu_2}{\nu_1} = \frac{\frac{1}{2\pi} \sqrt{\frac{2k_1}{m}}}{\frac{1}{2\pi} \sqrt{\frac{k_1}{m}}} = \sqrt{\frac{2k_1}{k_1}} = \sqrt{2}

Thus, the value of ν2ν1\frac{\nu_2}{\nu_1} is 2\sqrt{2}, which corresponds to Option C.

Frequency of Oscillation for Cut Spring Mass System | Physics PYQ Solution - JEE Challenger