Motion in Air Investigation

Task:

Design an investigation into a factor that affects the flight of an object in the air

Background:

A projectile is any object released into the air. When is in the air the object starts to release because of several factors.

Factors that affect the flightof anobject in the air:

The object: Shape and Size. If the shape or the size of the projectile vary, also will do it the air resistance so, this means that the projectile will travel less distance.

The Motion: Velocity and Inclination to Flow. The projectile has to travel at the same velocity and with the same inclination so the time cannot vary, but we are changing the distance we strech the elastic band so the velocity will vary.

The air: Mass, Viscosity, Compressibility, Gravity, Air Resistance. The gravity is the same because we make the experiment in the same place with the same gravity. The mass and the viscosity will be the same, so the projectile will have the same size and shape.

3 equations related to motion:

Vf = Vi + at: To calculate the final  of a projectile, we need to plus the initial velocity to the multipllication of accelerationper time.

Vav = (Vi + Vf)/2: To calculate the average velocity we need to plus the initial velocity to the final velocity and divided all into 2.

T= (Vf-Vi)/2: To calculate the time you have to subtract the final velocity into the inicial velocity and divided all into the acceleration.

Research question:

How does changing the force of release affect the distance travelled of a projectile in motion?

Hypothesis:

According to my background, I believe that depending how do you strech the elastic band, it will reach more or less distance. If you strech the elastic band 15 cm this means that you are putting a lot of force in the projectile and it will reach more distance. If you strech the elastic band 5 cm you are not putting many force in the projectile, so, it will reach a very low distance.

I will use the formula of the initial velocity to prove that when we strech more distance the elastic band, the distance is higher so the initial velocity will also be higher because the mass of the projectile doesn´t vary in any tests. Formula of initial velocity= Vf- at.

The shape of the projectile always will be the same, so the air resistance will always be the same and it wouldn´t affect directly to the experiment.

Variables:

Independent variable: Distance we strech the elastic band, which will be measured in centimeters using a ruler.

Dependent variable: Distance the projectile travels measured in meters using a tape measure.

Controlled variable: The surface area of the projectile, I will control it using the same projectile with the same area to all tests.  The air resistance, gravity, I will control it because I will make the experiment in the same place with the same gravity, 9,8 m/s2. The elastic band, I will use the same elastic band for all tests. The two sticks and the position of the base, so the sticks offer the same resistance. The distance between both sticks measure in cm using a ruler.

List of materials:

-          Elastic band

-          Two supports (sticks) of wood

-          Plastecine

-          A knife

-          Ruler

-          Measure tape

Method:

1.       Cut using a knife a piece of clay

2.       Measure using a ruler the distance between the two sticks and set the elastic band in the sticks.

3.       Pull the rubber band back 5 cm, 7, 9, 11, 13 and 15 cm (measure with the ruler the distance). 

4.       Throw the ball of clay and measure with the measure tape the distance it has travelled.

5.       Collect all the data in a table to make a graph.

6.       Repeat the same steps 3 times with all the different distances to get accurate results.

Table for the results of the distance the projectile after throwing it at different distances (of the rubber band)

Distance of band (where it is placed to were the projectile is) in cm
Times repeated		5	7	9	11	13	15
	1	19	132	379.5	515	544	567.5
	2	23	145	381	530	535.5	560.5
	3	28	139	375	519	540	572
	Average	23.333	138.666	378.5	521.333	539.833	566.666

Graph for the distance the projectile after throwing it at different distances (of the rubber band)

Evaluation

Although it was an easy experiment, we know that the results are not very reliable because the technique we used to through the ball was not very scientific.

Firstly the plasticine deformed with the air resistance, so in the last test the ball will have less volume than in the first one. To solve this problem, we will use a marble that doesn´t deformed because is made of plastic.

Other problem was that when we threw the balls, the angle was not the same for all tests, this could affect to our results so the graph is not completely correct. This happens because we pull back the elastic band and our hands probably moved. A solution to this problem would be to write a mark in the wall to know the distance we through the projectile from the floor, so we only have to pull back the elastic band to the mark on the wall and the angle will always be the same.

Moreover, the traveling distance we measure is probably not correct 100%. From 7 cm, the ball travels far from where we was and we could not calculated with our ruler because was only from 30 cm so we calculated the distance of one tile and we multiplied it with the tiles the ball travels. For example, if the ball goes 10 tiles far from where we threw the ball, we multiplied the distance of one tile by 10. This was not a very scientific technique, so for the next time we will use a meter to measure the distance with accuracy.

To conclude, I would say that our principal problem is the measurements that are not accuracy and affects directly to our graph so is the point we need to improve. 

 Conclusion

Our results have been good, as when the rubber band is at more distance, the tension is higher so it will go further, which means that the initial speed will be higher. We can see in our graph that the last values don’t have so much difference between them than the ones at the start, this can be due to the rubber band use, and that through the experiment it doesn’t have finally the same tension. Our hypothesis has been proven, so how longer is the distance of the end of the rubber band to where it is placed, the more distance it will travel (the ball). This could be a directly proportional relation, but I think that for so exact values is needed a higher quality experiment.

Not all of the equations or formulas included in the background (in the research part of the investigation) were used in our experiment or were completely relevant, but I think it is better to have them as a guide and to be able to relate different concepts. The one which is linked to the initial velocity is very important, because that is just what we are changing in our experiment; the initial velocity changing the tension of the band so that it shoots the projectile harder.

In my opinion, the method was well stated and clear. If you follow this method as it says you will have good results in your experiment. Having a clear, structured method is a very important part in science.

References:

Citycollegiate.com, (2015). EQUATIONS OF MOTION-FIRST EQUATION OF MOTION-SECOND EQUATION OF MOTION-THIRD EQUATION OF MOTION. [online] Available at: http://www.citycollegiate.com/kinematicsXb.htm [Accessed 31 May. 2015].

Exploration.grc.nasa.gov, (2015). Factors that Affect Aerodynamics. [online] Available at: http://exploration.grc.nasa.gov/education/rocket/factord.html [Accessed 32 May. 2015].

Physics.info, (2015). Motion - The Physics Hypertextbook. [online] Available at: http://physics.info/motion/ [Accessed 15 Jun. 2015].