Making sense of data.

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Coursework - Making Sense of Data

Introduction

The method used to collect the data was to fire projectiles from a launcher into a sandpit. The distance the projectile travelled was measured. For each projectile the angle of the launch was varied from 15 to 70o, from the horizontal. Twelve different angles were tested and three repeat readings were taken at each angle.

Five ball bearings with different diameters were used. The ball bearing was fired using a spring mechanism into a sandpit, which was at the same height that the ball bearing was launched from. The distance travelled was measured using a meter ruler.

Apparatus Diagram

Plan

  • From the raw results the mean distance travelled was calculated, giving an average reading using all the data.
  • From the diameter of the ball bearing the volume of the ball bearing was calculated - 4/3 * pi * radius3.  From this the mass can be calculated (using mass = density * volume).
  • The energy the spring provided was given as 0.1J. Using the mass this allowed the initial velocity to be calculated (initial velocity =sqrt (KE/0.5m)).
  • The initial velocity was divided into horizontal and vertical components using the sine and cosine rules combined with the angle of launch.
  • Knowing that the displacement vertically is zero, gravity is -9.8N/Kg and the initial vertical velocity the flight time can be worked out: time=2(initial velocity/gravity).
  • Assuming no air resistance the distance traveled should equal the time taken multiplied by the initial horizontal velocity. This allows a theoretical prediction of the distance travelled, which can be compared to the actual distance measured.

Prediction

The prediction is that the smaller ball bearings will travel further because the launcher provides the same energy to every ball bearing. Therefore the larger ball bearings will have a slower initial velocity as more energy is needed to accelerate them, counteracting gravity.

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The greatest distance should be achieved at around 45o with each mass of ball bearing because the horizontal and vertical components of velocity equal each other. Any angle above 45o will have too much vertical velocity and not enough horizontal force, therefore just going up and down, without gaining much distance. Angles less than 45o will have more horizontal force, but not the height, so will not be able to achieve the maximum distance, falling quickly to earth.

Graphs to plot

  1. Distance-angle with different data series for different ball bearings

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