The first law of motion states that an object at rest, will remain at rest until an outside object makes contact
Gravity is always acting on an object. Here, gravity is the only force acting on a till rocket, keeping it down on the ground
But in Space, since there is no gravity around, there is no force stopping the rocket. See, when a rockets launches, there is gravity and thrust both acting on it, but since there is no gravity in space, the rocket will thrust forward and continue traveling forever, unless an outside object collides with it.
If the rocket were flying on Earth, thrusters are needed to have the rocket accelerate, since gravity is always acting on it
Newton's Second Law* Law of Acceleration *
Mass/force/thrust is needed so it can be heavier than the other rocket ship.
The second law of motion states that the acceleration of an object is dependent on the mass of the object as well as the force applied
It has more mass so it is heavier.
This means that the heavier the rocket, or the more stuff a rocket carries, the more force or thrust is required to gain the maximum acceleration to propel it into space
The third law of motion states that for every action, there is an equal and opposite reaction involved
.... so more thrust and force is needed to counteract the gravity to have the rocket gain acceleration
Gravity is always acting on the rocket while on Earth....
In order for the rocket to launch, the exhaust gas is using force against the thruster, causing the thruster to push the exhaust gas out. This causes the rocket to move in the opposite direction of the exhaust gas.