Rockets overcome gravity through the principle of action and reaction described by Newton's third law of motion. According to this law, for every action, there is an equal and opposite reaction.
When a rocket is launched, it expels a high-speed stream of gases in the opposite direction to the desired motion. This stream of gases is created by burning rocket propellant, typically a combination of fuel and oxidizer. As the propellant is ignited and expelled through a nozzle at the rear of the rocket, it generates a force known as thrust.
The thrust force is directed downward and backward due to the expulsion of gases. According to Newton's third law, an equal and opposite force is exerted on the rocket in the upward direction, counteracting the force of gravity. This force, known as the rocket's weight or gravitational force, is the force acting on the mass of the rocket due to the gravitational pull of the Earth.
To overcome gravity, the thrust generated by the rocket's engines must be greater than the weight of the rocket. By producing a greater upward force, the rocket accelerates upwards, gradually gaining altitude and velocity.
In addition to thrust, rockets also utilize the concept of velocity achieved through continuous acceleration. As the rocket ascends, it gradually increases its velocity, reaching higher speeds. According to Newton's second law of motion (F = ma), the acceleration of the rocket is directly proportional to the net force acting on it. By increasing the velocity, the rocket counteracts the pull of gravity more effectively.
It's important to note that rockets also need to overcome other forces such as air resistance or atmospheric drag, which can affect their ascent. To minimize the impact of these forces, rockets are often designed with streamlined shapes and are launched vertically to quickly ascend through the denser parts of the atmosphere.
In summary, rockets overcome gravity by generating thrust through the expulsion of gases in the opposite direction, in accordance with Newton's third law of motion. The thrust force counteracts the force of gravity, allowing the rocket to ascend and eventually overcome Earth's gravitational pull.