The use of physics theories in various fields is making the life easier nowadays. The best part regarding this theories is that it makes sense to the people if it is explained in simple words other than complicating them. One of best application based theories in mechanics is the use of thrust force. It finds use in hydraulic lift, rocket repulsion etc.
Concept of Thrust Force
By the concept of pressure which says that 'pressure is the thrust applied per unit area'. This means that when a force is applied on an area, the amount of force that is applied on a unit portion of that area called the pressure on that area i.e. Pressure = Thrust Force/ Area.
In the same way we can say Thrust force = Pressure ✖ Area. Therefore we can say Thrust force is the product of pressure and area or by definition :- 'pressure applied on a unit area'. This means we can produce thrust force by applying pressure over an area. So as the thrust force can produce pressure, in the same way pressure can also produce thrust force.
Rocket Repulsion Concept
One of the important application of thrust force is regarding rocket repulsion. It is used in lifting rocket from ground by overcoming the gravitational force of attraction and making it reach the space.
Rocket requires high amount of fuel that burns causing high inflammation to the ground during its departure. This fuel plays an important role in lifting the rocket from the surface of earth. Infract, fuel is the only thing that give rise to thrust force.
This fuel can be treated as mass which escapes from the rocket when it burns inside the rocket. This escaped mass produces thrust force in direction opposite to the direction in which it escapes. For example, in case of rocket the fuel consumed escapes downwards therefore, the thrust force is applied in upward direction.
In case of rocket repulsion, Thrust force has totally different equation :- Thrust force = relative velocity ✖ rate of change of mass with respect to time.
Relative velocity over here refers to velocity of mass ejected or fuel ejected relative to main mass.
There are two cases which can be used to solve rocket repulsion problems :-
CASE 1 :- When rocket needs to be just lifted from ground
In this case, in order to lift rocket from ground, the thrust force acting on the rocket must be equal to the weight of the rocket acting downwards.
CASE 2 :- If rocket needs to reach the space
In this case, if rocket needs to enter the space, it must first overcome the gravitational force exerted on it by the Earth. This means that, the thrust force in this case will be greater than the weight of the rocket acting downwards. The thrust force in this case will be able to provide the required escape velocity(11.2 km/s) to the rocket to escape from the earth's gravitational pull.
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