Give the characteristics of shm.

Explanation

### Step-by-Step Solution:

1. **Definition of SHM**: Simple Harmonic Motion (SHM) is a type of periodic motion where an object oscillates around a mean position. The motion is characterized by a restoring force that is directly proportional to the displacement from the mean position.

2. **Acceleration and Displacement**: In SHM, the acceleration of the object is directly proportional to its displacement from the mean position and is always directed towards the mean position. Mathematically, this can be expressed as:
\[ a \propto -x \]
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