What is the basic law behind the rocket launch ?

Explanation

### Step-by-Step Solution:

1. **Understanding Rocket Launch**: A rocket launch involves the rocket expelling gases at high speed in one direction. This action is crucial for the rocket's movement.

2. **Action and Reaction**: When the rocket releases gases, it exerts a force on the Earth. According to Newton's third law of motion, for every action, there is an equal and opposite reaction. Therefore, the Earth exerts an equal and opposite force back on the rocket.

3. **Force Interaction**: The force exerted by the rocket on the Earth causes the rocket to move upwards. The more force the rocket applies downwards (by expelling gases), the greater the upward force it receives from the Earth.

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