Projectiles Practical Report

Projectiles Practical Report 1. Introduction Velocity is a vector measurement of the rate and direction of motion or, in other terms, the rate and direction of the change in the position of an object. [1] Velocity can be found many ways through various suvat Equations and their rearranged forms. For example v2=u2+2as in which the square of the final velocity can be found if you know the objects initial velocity, the acceleration and the distance travelled. Using such formulae makes it possible to test equipment, efficiently and accurately. . Aim The aim of this practical is to build and evaluate the performance of a marble launcher, this is done by first finding the velocity of the marble using the equation v2=u2+2as, this will be done by conducting an experiment to first find the vertical distance (s) the marble travels and acceleration due to gravity (a). This will then be used to find the time the marble will travel for at angles of 30o, 45o and 60o using the equation v=u=at, rear ranging this equation to find the time the marble will travel at will become, .Taking the value and doubling it will give you the time it takes to reach the peak velocity and return to rest. This value is then used to predict the range the marble will travel from a set angle via the rule Distance = Speed X Time. These distances will be compared to actual distances tested and evaluated. 3. Procedure 3. 1 Apparatus †¢ Protractor or set square †¢ Meter rule †¢ Small sand pit †¢ Safety spectacles †¢ Compression spring †¢ 1cm diameter plastic conduit †¢ 1cm diameter rubber bung to fit †¢ Marble †¢ Nail 3. 2 Method 1.Firstly the assembly of the launcher, after placing the nail through the pre-cut hole transecting the pipe, the marble is placed inside followed by the spring, the bung is fixed securely in the bottom of the pipe causing tension on the spring which is held until the pin is released. 2. Fixing the launcher to a clamp stand secures t hat during firing of the marble it will remain at the same angle. 3. Start the experiment by firing the marble vertically to find an average result for the distance the marble travels (Table 4. 1). 4. After this the results can then be used to find the Velocity of the marble. . Using the calculated velocity and suvat equations an estimation for the distance travelled by the marble and the time the marble travelled for can be found for set angles of launch measuring 30o, 45o and 60o. 6. Actual results are then compiled (Table 4. 2). 7. And compared to the estimates (Table 4. 3). 4. Results Table 4. 1: Table showing the mean height travelled by the marble Height travelled by marble (cm) 1 129 2 103 3 98 AVERAGE HEIGHT = 110cm or 1. 1m From this result the Velocity can be determined using the equation v2=u2+2as v2=02+2(9. 8Ãâ€"1. 1) 2=21. 56 v = 4. 64 ms-1 With this result for v the times for each angle can be calculated using the equation v=u=at, rearranging this equation to find the time the marble will travel will become, . and so for the angles 30o, 45o and 60o the calculations are as follows. 600) = = 0. 24s to 2 d. p 450) = = 0. 33 to 2 d. p 300) = = 0. 41 to 2 d. p To find and estimate a distance from the times found previously the value for time is used to predict the range the marble will travel from a set angle via the rule Distance = Speed X Time, speed we know to be 4. 4ms from earlier in the experiment. And time for this calculation is double that of the value found previously because we only worked out the peak velocity, doubling the time compensates for the time taken to reach the peak and the time taken to return to the sand pit. Lm 600) Distance = Speed X Time = 4. 64 x Cos60 x 0. 48 = 1. 93m 450) Distance = Speed X Time = 4. 64 x Cos45 x 0. 66 = 2. 17m 300) Distance = Speed X Time = 4. 64 x Cos30 x 0. 82 = 1. 90m These values are the estimates for the distance travelled by the marble from a launcher at set angles. Table 4. : Table showing the t esting of the launcher at set angles. Test 1 (m) Test 2 (m) Test 3 (m) Average (m) 600 1. 3 1. 4 1. 2 1. 3 450 1. 8 1. 8 1. 8 1. 8 300 1. 6 1. 6 1. 7 1. 63 The averages for each angle when calculated are then compared to the estimates made previously. Table 4. 3: Table showing the time taken, the estimated distance travelled and the actual distance travelled by the marble at set angles of trajectory. Angle of Trajectory Time (s) Estimated Distance (m) Actual Distance (m) 600 0. 24 1. 93 1. 50 450 0. 33 2. 17 1. 80 300 0. 41 1. 90 1. 65 5. Summary 5. 1 DiscussionThe practical was simple enough to evaluate the performance of a marble launcher. It did this efficiently and without major complication. The assembly of the launcher is straightforward with simple components and functions, the testing is easy to carry out, and the results found from the experiment are fairly accurate. 5. 2 Conclusion From the results it was found that the actual distance was less then the estimated distance in all three scenarios. The results did however show similarities between the two sets of data. Both sets showed a pattern where the 30o and 60o values were lower than the 45o value.These two results also appeared to be very similar values in both the estimated and actual calculations. 5. 3 Evaluation The experiments accuracy is fair but could be improved, due to the need for a person to operate the launchers release mechanism, consistency is lost during each firing of the launcher, this could be improved with a mechanical release mechanism or a different style of launcher for example a compressed air powered device. 6. Reference [1] Andrew Zimmerman Jones. 2012. Velocity – Definition of velocity. [WWW] http://physics. about. com/od/glossary/g/velocity. htm. (17 October 2012)