free fall with air resistance

Physics 2111
Student
professor

Lab #3 Free Fall With Air Resistance

The experiments in this lab will demonstrate the relationship between air resistance and acceleration of an object during free fall.To calculate the acceleration you will use the following formula: 2 delta x/ t^2 In this lab you will drop coffee filters from a height of one meter. You will measure their acceleration by measuring the vertical distance and the time that coffee filters take in traveling that distance.
Objectives
After completing this lab, you will be able to:
1. calculate the acceleration of falling object and discuss the effect of air resistance on free fall by drawing graphs between mass versus acceleration.
2. calculate the acceleration of and discuss the effect of air resistance on free fall by drawing graphs between areas of cross-section versus acceleration.
Experiment Materials
You will do this experiment with items from your Laboratory Materials List. You will need:
One pack of coffee filters
Meter-stick or metric measuring tape
Stop watch (with count of at least 0.01 sec.)
In Part A, you will study the effect of mass on acceleration in free fall of coffee filters.
You will start with one coffee filter, which you will drop and measure the time of drop for a known height (1 meter). You will repeat this process four times and record the data in Table A. You will then use two filters, which have to be of the same size as the single filter and also stuck together. You will make four more measurements of time by dropping two filters for the same height. You will then do this again for three filters and then with four filters. Once you have all the data you will graph the mass verses the acceleration with Excel. From the discussion of air resistance you will comment on whether the graph is correct or not and what it tells you about air resistance.
Directions:
1. The average mass of one coffee filter is one gram.
2. Make two marks at the vertical height of one meter. Use these marks for finding the time of free fall of coffee filters for a height of one meter.
3. Find the least count of your stopwatch. Use this stopwatch for measuring time and take observations to the smallest scale division.
4. Drop one coffee filter four times and find the time t it takes for the coffee filter to drop one-meter in each trial. Record these observations.
5. Now stick two filters together. Drop these filters four times. Find the time t it takes for the coffee filter to drop one meter in each trial. Record these observations.
6. Repeat again with three filters, four filters, and five filters and note the time of a one meter drop in each trial.
7. From the data compute the acceleration of coffee filters.
8. Plot mass versus acceleration from the experimental data in Data Table A. Using Excel, draw a smooth graph and interpret the graph.
In Part B you will measure the affect of area of cross section (of open side) on air resistance. To do this you will start with a coffee filter that is not very flared out. You will need to measure the acceleration like you did in Part A. You will then measure the diameter of the coffee filter across the top. This will let you calculate the area of the filter.
You will then flatten out the coffee filter a bit and repeat the measurement of the acceleration and the area again. You will repeat this four times until the coffee filter is completely flat. Using Excel, you will graph the area verses acceleration. In your report, discuss the effect of area on the acceleration.
Directions:
1. Measure the diameter of the open section five times at different places. Find average diameter, and calculate area of cross-section using formula (A = p r2, where r is the radius of the circle). Drop this filter four times and find the time t the coffee filter takes for one-meter drop in each trial. Record these observations in Data Table B.
2. Flatten out the coffee filter a little bit and repeat step 1.
3. Repeat steps 1 and 2 three more times until the coffee filter is completely flat.
4. From the data, compute the acceleration of coffee filters.
5. Plot area versus acceleration from the experimental data in Data Table B. Draw a smooth graph and interpret the graph.

Mass of 1 filter = 1.0 g
Distance Δx= m (Should be 1 m)

Table A

Mass
Time 1
Time 2
Time 3
Time 4
Average Time
Average Acceleration

(g)
(s)
(s)
(s)
(s)
(s)
(m/s2)
1 coffee filter
1.0 grams
1.1
1.1
1.09
1.07
1.09
0.92
2 coffee filter
1.0 grams
0.77
0.78
0.87
0.78
0.8
1.25
3 coffee filter
1.0 grams
0.7
0.69
0.74
0.69
0.71
1.4
4 coffee filter
1.0 grams
0.61
0.65
0.61
0.56
0.61
1.64 5 coffee filter
1.0 grams
0.53
0.6
0.58
0.61
0.58
1.74

Table B

Area
Time 1
Time 2
Time 3
Time 4
Average Time
Average Acceleration

(cm2)
(s)
(s)
(s)
(s)
(s)
(m/s2)
Least flared out
14
1.2
1.7
1.6
1.4
1,5
0.69

16
1.41
1.27
1.33
1.34
1.33
0.75 18
1.41
1.43
1.39
1.49
1.43
0.7 19
1.52
1.55
1.53
1.56
1.54
0.65
Most flared out
20
1.79
1.85
1.91
1.88
1.86
0.54

In this experiment I saw how much the shape of an object like a coffee filter can affect how it free falls. The air displacement is greater the more flat the object is. Through trail testing I saw the average time and acceleration of each displacement and some stacked inside each other. The minimum stack that was used was 1 and the maximum was 5. Then I took one filter and slowly flattened it out in intervals of 5 and saw how much the time was changed. I would like to further do this experiment with different objects and see how they displace air and how their time and velocity changes.