Normal Reaction and Weight Measurement
The normal reaction is a force exerted by a surface to support the weight of an object resting on it. This force acts perpendicular to the surface and prevents the object from falling through the surface. It is crucial in measuring weight and holding objects over the Earth's force.

Measuring Weight:
- When an object is placed on a surface, the normal reaction force exerted by the surface balances the weight of the object acting downwards.
- By measuring the normal reaction force, we can determine the weight of the object. This is because the normal reaction force is equal in magnitude but opposite in direction to the weight of the object.

Holding Objects over Earth's Force:
- When we hold an object in our hands, the normal reaction force exerted by our hands balances the weight of the object acting downwards due to gravity.
- Without the normal reaction force, the object would fall freely towards the Earth's center.
- By applying a force equal to the weight of the object in the opposite direction, we can hold the object stationary.

Conclusion:
Normal reaction plays a crucial role in weight measurement and holding objects over Earth's force. By understanding and utilizing this force, we can effectively measure weight and prevent objects from falling under the influence of gravity.