Lab #5 (trajectories) Daniel Guzman

Daniel Guzman

Physics 4A.

Lab#5 Trajectories




The purpose of this lab was to understand the phenomena of projectile motion and the interesting components of it. For instance, we wanted to understand how the x and y components of the motion of a projectile are totally independent, and how they affect and describe the motion of the projectile.

The apparatus of this experiment consisted of track a sphere, a sheet of carbon paper, a sheet of white paper, a woof board, and a clamp. The set up of this experiment was somehow easy due that the same set up was used for most of the experiment. The first thing was to set up the track were the little sphere would roll, in order to set up the track we used a clamp to keep it in place, then on the track we used tape to mark where the sphere was going to start every time. After setting the track we proceeded and put the carbon paper underneath the white sheet of paper so the position of the sphere would be marked as it hits the floor. For the second part the set up was pretty much the same the only thing that would change was that instead of putting the carbon paper on the floor it was put on the wood board that laid against the table at some angle, so the ball would now hit the board instead of hitting the floor at the end of its trajectory.

Experimental procedure.
The first thing to do for this particular laboratory was to set up the apparatus, once the apparatus was set up, we proceeded and let the sphere slide down the slope and recorded 5 different times where the ball landed on  the white sheet of paper using the carbon paper. Once these recording were made we proceeded and measure the horizontal distance that the ball traveled. Once this is measured one also had to measure how high was the ball when it stating to move as a projectile, after these measurements are done one could proceed to second part where one would use the wood board, so the sphere would hit the board instead of hitting the floor. For this part some calculation had to be made so one would know where the sphere should hit the board and based on this one would know where to place the carbon paper and the white sheet of paper.


Calculation for first part

calculations to find the initial velocity in the x direction once the sphere starts moving as a projectile

Calculations for part two to find the distance where the sphere would hit the board, the angle was measured using a cellphone and the vox was obtained for the first set of calculations

comparing the average value to the theoretical value obtained

The average from the experimental value was 0.89978 meters and the theoretical found was 0.904. when comparing them I used the percent error and found that the percent error between them was 0.4%,

Calculated propagated uncertainties for the first and second cases


For the first case the propagated uncertainty was calculated for the v initial in the x direction and i calculated the uncertainty for delta x to compare to the uncertainty used when finding the propagated uncertainty for vo initial in the x direction.

for the second case the propagated uncertainty was calculated for the distance where the ball hits the board when it is moving as a projectile.

Conclusion : for this experiment the experimental distance and the theoretical distance where the sphere should hit the ball where very close to each other, one can support this because the percent error between the experimental result and the theoretical result was only 4 percent, which lets one assume that the experiment was carried out correctly due that the results obtained in the first part of it where very important when deriving the expression that would allow me to calculate the theoretical displacement. The sources of error in this experiment might come from how i measured the position of the sphere when it hit the sheet of white paper that was on top of the carbon paper. Another source of error might come from measuring the angle correctly due that the distance where the sphere is going to hit it depends on it.