Projectile Motion Lab Report

Lynch, Mary

Partners: Hicks, Black; Kroeger, Erik; Carper, Mike

Motion: Projectile Motion

TA: Meghna Bhattacharya (Section 4)

February 28, 2017

OBJECTIVE

This object of the experiment was to demonstrate the average distance the ball traveled when shot from the spring gun. The test was used to show how the angle of elevation and initial velocity will affect where the ball is estimated to land. Using data collected on average distance found in part one of the experiment, you were then able to calculate time, when y=0 and yo= the distance from the spring gun to the floor, for part one using the equation Y=Y0+V0yT+1/2at2 (equation 1). Next, by using your average x you could calculate v0 using xavg = v0cosθt= v0 t (equation 2). Then, using the same v0 in part 2 you solve for t using equation 1 and then find xtheo using xtheo=v0cosθt (equation 3). Lastly, measure X, and find the average and then compare xtheo to xavg using | xavg-xtheo/xtheo | x 100 (equation 4).

EQUIPMENT AND PROCEDURE

In order to produce this experiment, you began by setting up the angles at which the spring gun would launch the metal ball onto the ground to measure its distance. The spring gun was placed, ideally, at table

height and would then launch the ball onto the ground towards a target. The target was a piece of white computer paper. It was shot first in order to estimate where the target would need to be placed. Once the target was placed in the correct area, a piece of graphite paper was added to the top of it so that, when the ball landed, it would mark the computer paper in order to get an accurate measurement point for the meter sticks. In order to make sure that the ball was being launched the same for every trial, the experimenter would cock the gun to the longest range, the third detent. The spring gun would be fired, the mark made on the paper, and then you would measure the distance of the mark from the origin. The origin consisting of the position of the spring gun from which the ball had been fired. This was repeated 6 times in order to find the data for part 1. The independent variables were the high from the group to the spring gun, the initial velocity, the angles at which the fun released the projectile, and the time. The dependent variables were the Xexp and Xavg. The differences between Part 1 and Part 2 of the experiment were the angles from which the ball was launched. In part 1 the ball was launched at an angle θ=00 whereas in part 2 the angle was a measurement between θ=200 or V=300.

DATA AND ANALYSIS
Raw Data:

Calculated Data:

Avg=(sum of all x’s)/ (numbers of trials)
% error= equation 4

CONCLUSION
After observing how the angle measurement of the spring gun affected the distance measured on the ball, it is a safe argument to say that the distance the ball traveled is heavily influenced by the angle at which it was shot.

This is prove through the data as well as the equations used to find the variables. One example of this is once you had found t and vo (equations 1 and 2) you could then calculate the the theoretical xavg without even testing it first. The independent variables were the angles manipulated by the experimenter. Proof that the independent variables were the angles would be the fact that all of the dependent variables, time and xexp, differed between part 1 and part 2 and the only facts that differed in part 1 and 2 were the angles at which the ball was

shot
There is not a definitive answer about correlation between xtheo and your results mainly due to factors such as air resistance, inaccurate measurements, different numbers of significant figures, or even if the speed at which you released the spring could have affected your data.
QUESTIONS
If a ball has twice the mass but the same initial velocity, what effect would this have on its displacement (neglect air resistance)?
There would be no effect on the object’s displacement when you neglect air resistance an objects mass could be 10 times the original and it should still land in approximately the same spot.
Consider the following statement: When a rifle is fired horizontally, the bullet leaves the barrel and doesn't drop at all for the first 75 meters of flight. Is this statement true?
This statement is not true because the ball drops due to forces such as gravity and air resistance acting upon the ball and forcing it downwards.
What is the acceleration of a projectile fired vertically upwards? Is it positive or negative? Sketch your coordinate system.

What is the acceleration of a projectile fired vertically downwards? Is it positive or negative? Use the same coordinate system you used for Question 3?
The acceleration would be the same because it is following gravity and has very little air resistance.
Determine the standard deviation for xi for part 1. (Refer to appendix A)

Determine standard deviation for xi for part 2.