What provides the restoriing force for simple harmonic oscillations in the following cases? (i)simple pendulum (ii) spriing (iii) column of mercury in U tube.

Explanation

To determine what provides the restoring force for simple harmonic oscillations in the given cases, we can analyze each scenario step by step:

### Step 1: Simple Pendulum
- **Explanation**: In a simple pendulum, when the pendulum is displaced from its equilibrium position, the force acting on it is due to gravity. The component of the gravitational force that acts along the path of the pendulum's swing provides the restoring force.
- **Restoring Force**: The restoring force is provided by gravity.

### Step 2: Spring
- **Explanation**: In the case of a spring, when the spring is either compressed or stretched from its equilibrium position, it exerts a force that tries to return it to that position. This force is due to the elasticity of the spring, which follows Hooke's Law.
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