An object of mass [tex]$m=8.0 \, \text{kg}$[/tex] is attached to an ideal spring and allowed to hang in the Earth's gravitational field. The spring stretches [tex]2.2 \, \text{cm}[/tex] before it reaches its equilibrium position. If it were now allowed to oscillate by this spring, what would be its frequency?

A. 3.4 Hz
B. 0.52 Hz
C. 1.6 Hz
D. [tex]0.28 \times 10^{-3} \, \text{Hz}[/tex]



Answer :

Let's break down the steps to determine the frequency of oscillation for the given mass-spring system.

### Step-by-Step Solution

1. Given Data:
- Mass, [tex]\( m = 8.0 \)[/tex] kg
- Stretch (displacement), [tex]\( x = 2.2 \)[/tex] cm, which needs to be converted into meters:
[tex]\[ x = 2.2 \text{ cm} = 2.2 \times 10^{-2} \text{ m} = 0.022 \text{ m} \][/tex]
- Acceleration due to gravity, [tex]\( g = 9.81 \)[/tex] m/s[tex]\(^2\)[/tex]

2. Find the Spring Constant (k):
Using Hooke's Law, where the force [tex]\( F \)[/tex] exerted by the mass is balanced by the restoring force of the spring:
[tex]\[ F = kx \quad \text{and} \quad F = mg \][/tex]
Therefore,
[tex]\[ mg = kx \][/tex]
Solving for [tex]\( k \)[/tex]:
[tex]\[ k = \frac{mg}{x} \][/tex]
Substituting the given values:
[tex]\[ k = \frac{8.0 \text{ kg} \times 9.81 \text{ m/s}^2}{0.022 \text{ m}} \][/tex]
[tex]\[ k = 3567.27 \text{ N/m} \][/tex]

3. Determine the Angular Frequency [tex]\( \omega \)[/tex]:
The angular frequency [tex]\( \omega \)[/tex] is given by:
[tex]\[ \omega = \sqrt{\frac{k}{m}} \][/tex]
[tex]\[ \omega = \sqrt{\frac{3567.27 \text{ N/m}}{8.0 \text{ kg}}} \][/tex]
[tex]\[ \omega = 21.12 \text{ rad/s} \][/tex]

4. Convert Angular Frequency to Frequency:
Frequency [tex]\( f \)[/tex] in Hz is given by:
[tex]\[ f = \frac{\omega}{2\pi} \][/tex]
[tex]\[ f = \frac{21.12 \text{ rad/s}}{2\pi} \][/tex]
[tex]\[ f = 3.361 \text{ Hz} \][/tex]

### Conclusion

Hence, the frequency of oscillation for the given mass-spring system is approximately [tex]\( 3.4 \)[/tex] Hz.

So, the correct answer from the given options is [tex]\( 3.4 \)[/tex] Hz.