What Causes the Action Force When a Rocket Rises?

The action force when a rocket rises is caused by the rocket expelling gas out of its engine. The rocket reacts by moving in the opposite direction and lifting off from the launch pad.

A launching rocket follows Newton's third law, which states that every action has an opposite and equal reaction. The controlled explosion inside the rocket's engine is the pressure that creates the force. The pressure pushes the rocket one way and the gas the other way. The rocket lifts because the thrust (expelling of gas) from the engine is greater than the mass of the rocket. An unbalanced force is exerted. The amount of force is determined by the mass of the burned rocket fuel and by how fast the gas is expelled from the rocket. The motion is equal to and in the opposite direction of the force.