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Help w/ review of lab conclusion

  1. Oct 18, 2006 #1
    I am in a calculus based college level Physics I class. We're doing a lab on projectile motion. He is a stickler for grading the labs and just wanted to make sure everything is ok. My problem is that my conclusion seems awful short, but all that is asked calculate and measue the range and calculate the % diff.

    This labs purpose was to determine the initial speed of a projectile and then use the initial speed to predict the range of a projectile fired at an unknown angle. It is easy to see how England was able to have a dominate navy based on equations used in lab. As long as enough quantities are known, anyone could reasonably make a prediction of a projectile in motion with time, distance in vertical and horizontal ranges, angle, and velocity.

    The actual range of our experiment is 2.672m and the calculated range was 2.68m. This gave a % difference of only 0.23%. This is an excellent result given the amount of human error that could be made. If any error was made in calculating the initial velocity the second part of the lab would reflect this error. Some sources of error that could have been made was the length measurements with the meter stick and air resistance was not takin into consideration. The mechanism that fires the projectile gets weaker over time thus maks the firing inconsistent and causes the initial velocity to vary. Rounding errors and improper use of the equations could lead to error as well.​

    I just want to know is this a worthy conclusion? Am I missing something? I don't want to make it wordy and full of BS just to make seem like it's a long conclusion.
  2. jcsd
  3. Oct 19, 2006 #2


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    Real life ballistics is much more complicated than just considering projectile motion. Air resistance have a considerable contribution and needs to be evaluated for different shapes of projectiles. If the range is long one need to take the rotation of the earth into effect, which is lattitude dependent. Also the deviation depends on the direction of firing due to the rotation of the earth. Wind can deflect a projectile over along range. Another factor is the variation in the value of g over the surface of the earth that needs to be taken into account. If the projectile spins it will also be deflected due to the Magnus force.
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