Lab #1 - This is a lab report, lab report #1, The physics Lab-Picket Fence. PDF

Preview

Summary

This is a lab report, lab report #1, The physics Lab-Picket Fence....

Description

The Physics Laboratory-Picket Fence Introduction: The purpose of this lab was to measure the acceleration by means of two methods, position vs time graphs analysis and the speed vs time analysis which helped to determine the acceleration. This will be done by making an object fall 6 times and comparing and contrasting the slope of each trial, the slope should be around 9.8m/s^2. Apparatus: Computer with PASCO interface and PASCO with the capstone surface,and the photogate on a stand, and lastly the picket fence. Procedure: Part I: Experimenting with Capstone: ● Set up the photgate on the edge of the table, refer to figure 1. In order to avoid the damage that can happen to the picket fence use foam pad for smooth landing. ● Connect the photogate to digital input 1 to the PASCO interface. Refer to other inputs for future reference. ● Test if the photogate is working properly by checking the red indicator on the back of the photogate, if the light blinks it is working properly if it is not blinking check the power button. ● Open PASCO on the computer and open hardware setup menu on the left and select the correct input. The setup timers menu should appear. Part II: Plotting the data in excel: ● Open excel and make scatter plot of velocity vs time and then click on the plot and choose select data and add to the other runs. ● For each trial fit to the best line fit and do linear and add the trendline to the plot. Add y=mx+b to each trial, m is slope and y is y intercept. ● Also, use the data from last trial and make an graph of distance vs time and include the trendline and use appropriate units. Part III: Further data analysis: Reproducibility and Distributions: ● Compare equation 1 to 6 and see that the value of slope is considered as acceleration. Record these values in a new table and find the average in excel by typing =average( to find the average of 6 trials. Acceleration 9.7681 9.7047 9.7537 9.8132 9.7644

9.6993 9.750566667 (average of the 6 above done in excel) 0.03908016 (standard deviation of the mean) ● Yes, I did get a fairly close accepted value to 9.8m/s^2. ● Find the standard deviation in the excel by typing “=stdevp” and hit enter, Refer to the results in the table above. ● Calculate the F and the Error Propagation. ● Refer to the calauctions under data for the F and the error propagation. Precautions: This  experiment could have been done better if more exact results were required, then the other variables need to be controlled such as air conditions, altitude and presence of other intervening forces has to be measured and controlled. Source of Errors: There were few source of errors in this lab, first there could have been an error due to the resistance in air affecting the time of fall, also variations of height (altitude) could have influenced the pressure of air and therefore adding another force to the system, and firmly other forces such as possible magnetic or electric forces were disregarded. Data:

Calculations: Equation: F=m*g F=48.5*9.75 F=472.875 N

Equation: = 472.875 = 1.95

√(

0.05 2 ) 48.5

)2 + ( 0.039 9.75

Calculated force: 472.875+/-1.95 Questions: 1. Looking at the data, you should notice that the time difference between successive data points is smaller and smaller the farther the picket fence falls. Why is this? The point is getting smaller and smaller the farther the picket fence falls, it is because as the picket fence falls downwards the velocity increases and it takes less time for the sensor to catch the movement. 2. How does the computer know the velocity when all it is measuring is time? Hint: what is the other part of the equation for average velocity? The computer know the velocity when all it is measuring is time is because from the data the distance traveled can be calculated between each picket and from this we can calculate the velocity of the picket fence using the equation v=d/t and it can be easily done in excel. 3.. If we want the slope to be the acceleration, which variable, velocity or time, goes on the x-axis? Why? In order to get the slope to be the acceleration, time goes on the x-axis because delta (a)=delta(v)/delta(t), the denominator is change in time and it has to be in the x-axis by definition of the slope. 4. Describe in words the shape of the velocity vs. time graph. (Does the slope stay constant? Is the Y-intercept zero?) The shape of velocity vs time graph stays similar the slope stays constant and the y intercept is not zero.

5. Describe in words the shape of the distance vs. time graph for the free fall. How should this look (linear, quadratic, etc.)? The shape of distance vs time graph for the free fall looks linear because of the slope and the velocity is positive therefore, it is moving in the positive direction. 6. Look at your list of 6 slope values (i.e. acceleration values) and, in one or two qualitative sentences, report how reproducible your acceleration results appear (e.g. very similar values, widely varying from one trial to the next, etc.). The reproducible in my acceleration results appear to be very similar values. The slopes are close values to each other therefore, the acceleration is the same. 7. Is your standard deviation low when compared to the value of your average? As a rough guideline, a standard deviation less than 10% of your average is OK (but the lower the better!). Does this standard deviation seem reasonable with what you put for your quantitative description of reproducibility in Question 6? This shows how standard deviation is a measure of reproducibility. Yes, my groups standard deviation is low when compared to the value of the average. My groups standard deviation is 3.9% which is less than 10% expected standard deviation. And yes we have the quantitative description of reproducibility is in this experiment. 8. Looking at this equation, what would the standard deviation be if all of your measured values were the same? Explain. If all the standard deviation be 0 if all the measured values were the same because we don't have any deviation since all the values are same it would result in 0 deviation. 9. It is very useful to understand the effects of errors, both to prevent them and to account for unexpected results. When you drop the picket fence, the markers are perpendicular with the photogate beam. How your results be affected if the picket fence was dropped at an angle through the photogate? If the picket fence was dropped at an angle through photogate then it will not give proper data needed to find the acceleration. There will be no relationship between time and the distance infrared sensor which shines through the picket fence. 10. Using calculus, how do you determine (1) velocity from position, and (2) acceleration from position? Using calculus, we can determine velocity from position by the “first derivative” of the position with time equation, we can get the velocity. and the acceleration from position can be obtained from the “second derivative” of the position with time equation, we can get the acceleration/ Results and Discussion: This lab was done to find the acceleration due to gravity of each trial and the average acceleration of all six trials was calculated. The calculated average acceleration of the experiment group(my group) was 9.75m/s2 , which is close to the standard average of 9.8m/s2 , with an experimental error of only -0.5%. Also the standard deviation was 3.9% and it was expected to be lower than 10%. Using this information the force was calculated and it was 472.875+/-1.95 and this was obtained from the equation F=MG and calculated the corresponding error propagation due to g and m. A good reproducibility in this lab is ensured because the sources of error, such as other forces involved are very small compared to the force of gravity, therefore this experiment can easily be replicated and similar result can be expected....