Motion Lab Report

Carlos Pita
Aurora Martínez
María Victoria Rodríguez
Beatriz Pérez

RESULTS

Aluminium paper ball: 3,54g

The elastic band was stretched 10cm

	Table to show the distance the ball reaches (m)
DEGREES (º)	TRY 1	TRY 2	TRY 3	AVERAGE
0	2,80	2,73	2,94	2,82
20	3,80	3,91	0,80	2,84
45	9,10	8,90	9,90	9,30
60	5,10	5,20	7,20	5,83
80	3,00	2,80	2,30	2,70

Conclusion: As the graph and table shows the optimum angle would be 45º as it is when the ball reached its maximum length. If we take into account the anomalies as for example would be 0.80 metres at 20º the optimum angle will also be 45º. The yellow line shows this peak observed in the graph.

Also in the graph we can observe differences between the first two attempts and attempt 3 which probably is when we committed some mistakes as there is a huge difference from the lowest value to the highest value: from 0.80 to 9.90 (this difference is not presented in attempt 1 neither in attempt 2).

Afterwards the shots of 60º reach much higher distance than the others. In addition to this the other angles have lengths quite similar.

Also to obtain clearer conclusions it could have been a good idea to use different masses for the aluminium ball and to change the length of stretching the rubber band.

I conclude that majority of the experiment was well done as it resulted the optimum launching angle was the one researched.

We can determine the range of a projectile (displacement in horizontal direction) through the equation R . R is the range of the projectile and vi is the initial velocity.  is the launch angle and g gravity. Knowing the distance reached of the projectile could be very interesting when changing the angle of release or the speed. If we increase the launch speed, the range will increase. However, if we increase the angle of release, the range will be very low.

R= 10,2 meter.  We observe how 45º is the optimal launch angle as 10,2 is very close to the result where we obtained the higher range, 9.90 m.

Evaluation: We had some problems during the development of the experiment. Firstly, we didn’t exactly know how to make the object throw the ball, but finally we learned how to place the materials to throw the ball correctly. We also had timing problems; as we spent too much time learning how to work out the catapult, we didn’t had time to throw the ball 5 times, but instead we did it 3 times, therefore our results are not as accurate as we wanted them to be. We could have obtained a more reliable catapult from a specialised shop, however it would have cost us too much money. Another problem we had was that the clamps did not stay still, so it ended up influencing how the ball reached, therefore a solution for this would be either use something else such as a specialised device or make sure it stays still by holding it ourselves, as we did not know any form to attached them more securely without doing it ourselves. In addition, the ball was deflected back when it reached the ceiling, so as a solution for this we had to go somewhere outdoor, such as the playground. Finally, in more than one occasion we might have measured the length which the ball reached at the second bounce instead of the first, however we do not think that this human error has other solution rather than paying more attention to the ball. In fact, if we had used a camera maybe we could record distance more accurately.

References:
General Launch Angle. (2014). Boundless. Retrieved from https://www.boundless.com/physics/textbooks/624/two-dimensional-kinematics-3/projectile-motion-42/general-launch-angle-229-6255/
Physicsclassroom.com,. (2015). Maximum Range. Retrieved 16 April 2015, from http://www.physicsclassroom.com/mmedia/vectors/mr.cfm

Vista, T. (2015). Projectile Motion Formula | Formula for Projectile Motion | Formulas@TutorVista.com. Formulas.tutorvista.com. Retrieved 16 April 2015, from http://formulas.tutorvista.com/physics/projectile-motion-formula.html

Fitzpatrick, R. (2015). Projectile Motion with Air Resistance. Farside.ph.utexas.edu. Retrieved 16 April 2015, from http://farside.ph.utexas.edu/teaching/336k/Newtonhtml/node29.html