# Please help me with my Introduction ? I would really appreciate it!

1. Oct 12, 2009

### lockieleonard

Hi,

This is an introduction that I have written for my assignment that is about a bottle rocket experiment, so could you please read through it and correct the theory or the grammer mistakes if there are any. Also could you please give me an advice if any sentence can be made any better. I will really appreciate it. Thanks In advance.

Here is the introduction:

The purpose of this experiment was to confirm Newton's three laws of motion by the analysis of the motion of a bottle rocket moving in the air with net friction, gravitational and thrust force. This experiment was also done to find the best water/air ratio that gives the optimal flight height of the bottle rocket.

Force is defined as a push or pull that is exerted on an object, it can give energy to an object causing it to start moving, stop moving, or change its motion. Forces occur in pairs and can be either balanced or unbalanced. Balanced force occurs when number of forces that are equal and opposite in direction act on a body simultaneously causing no change in its motion. The resultant of these forces is zero. Unbalanced force occurs whenever two unequal forces with different strengths work against each other. An object with an unbalanced force is an object with a non-zero net force.

Pressure is a type of force. In this experiment, it plays an important role in launching the bottle rocket. Other types of forces include: Gravitational force - the force which attracts massive particles towards one another. It is the force that makes things falls to the ground.
Thrust force: the force that comes from the pressurized water and the air inside. Weight force: the vertical force exerted by a mass as a result of gravity.

In this experiment, the bottle rocket's motion mainly depends on Newton's three laws of motion since??? there are other things that also come into play such as outside or ambient pressure.

Newton's first law state that "Objects at rest remain at rest and objects in motion remain in motion in a straight line unless acted upon by an unbalanced force". During the experiment, this law is best demonstrated at the time just before the launch of the bottle rocket. For example, when the bottle is at rest, its weight force equals the gravity force, therefore there is no net force pushing the object anywhere, hence the bottle remains stationary. However, when the thrust force generates and become greater than the gravity force, an unbalanced force is formed and the bottle experiences an upwards pushing net force that causes it to rise.

At that same time, Newton's third law which states "For every action there is an equal and opposite reaction", is best applied when the forces of the built up air pressure and the water which push out through the nozzle at the bottle's tail create the action force, a reaction force is then created and the rocket is propelled in the opposite direction.
The thrust force that pushes the bottle rocket upwards is formed by the bottle's mass and the net acceleration of the bottle. This demonstrates the second law of Newton which states that "If an unbalanced (net) force acts on an object, that object will accelerate (or decelerate) in the direction of the force, through the relation, F=ma". This law is also demonstrated when the bottle starts to accelerate upwards and travels through the air, the thrust force pushing the rocket upwards constantly decreases because the pressure in the bottle decreases as the water and the gases inside the bottle starts to escape to the surrounding to equalize the pressure inside the bottle with the outside one. The mass of the bottle also decreases as it loses water. Therefore the acceleration also starts to constantly decrease. The bottle then stops accelerating when the thrust force equals the gravity force.

As the thrust force equalize the gravitational force, the bottle stops for a very short period of time in the air. At this time Newton's first law is demonstrated.

The thrust force continues to decrease, however the opposite force (i.e. the gravitational force) is constant, and hence the object lands back on earth because the gravity force becomes greater than the thrust force.

After that the gravitational force takes over the thrust force and pulls the bottle down to the ground. Newton's first law is demonstrated here as the bottle was at rest and then was pulled to the ground as result of a net force that resulted from unbalanced forces (i.e. gravitational and thrust force). At this time, Newton's second law is also demonstrated as the force that pushes the bottle down come from a net acceleration due to the gravitational acceleration on the bottle which is around 10 ms2. The bottle's mass doesn't affect the force as the mass is constant when the bottle lands back because all the water has already escaped.

In this experiment specialized equipments is used such as the clinometer and the bicycle pump. The clinometer is a compact hand held level used for approximating angles of elevation or depression and/or percentage slopes. The bicycle pump is a mechanical device that moves fluid or gas by pressure or suction.