2) A mass $m$ hangs from a massless spring connected to the roof of a box of mass $M$. When the box is held stationary, the mass–spring system oscillates vertically with angular frequency $\omega$. If the box is dropped and falls freely under gravity, how will the angular frequency change?

A) $\omega$ will be unchanged
B) $\omega$ will increase
C) $\omega$ will decrease
D) Oscillations are impossible under these conditions.
E) $\omega$ will either increase or decrease depending on the values of $M$ and $m$.
1. **Understanding the problem**: We have a mass \( m \) hanging from a massless spring connected to the roof of a box of mass \( M \). When the box is stationary, the mass-spring system oscillates with angular frequency \( \omega \). We need to determine how the angular frequency changes when the box is dropped and falls freely under gravity.

2. **Angular frequency in a stationary frame**: When the box is stationary, the angular frequency \( \omega \) of the mass-spring system is given by:
   \[
   \omega = \sqrt{\frac{k}{m}}
   \]
   where \( k \) is the spring constant.

3. **Free-fall condition**: When the box is dropped, it falls freely under gravity. In this scenario, both the box and the mass \( m \) experience the same gravitational acceleration \( g \). This means that in the frame of the box, the mass \( m \) is effectively in a gravity-free environment.

4. **Oscillations in a freely falling frame**: In the freely falling frame of the box, the only force acting on the mass \( m \) is the restoring force of the spring. The gravitational force does not affect the relative motion between the mass \( m \) and the box.

5. **Angular frequency in the freely falling frame**: Since the gravitational force is not affecting the relative motion, the angular frequency of the mass-spring system in the freely falling frame remains the same as it was when the box was stationary. Therefore, the angular frequency \( \omega \) in the freely falling frame is still:
   \[
   \omega = \sqrt{\frac{k}{m}}
   \]

6. **Conclusion**: The angular frequency \( \omega \) of the mass-spring system does not change when the box is dropped and falls freely under gravity. Thus, the correct answer is:
   \[
   \boxed{\text{A}}
   \]