Lab^N 5 - lab PDF

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FRICTION

Abstract/Introduction: The objective of this lab is to understand the concept of friction and also to show how materials incline can affect friction forces as to how it moves an object. Friction is a significant power, with positive and negative ramifications. At whatever point two articles slide along one another, grinding is included; regardless of whether a skier is sliding down a cold incline, or a box is hauled over the floor. On the positive side, contact between the street surface and the vehicle tires is the thing that keeps the vehicle moving along an interstate. On the negative side rubbing lessens the proficiency of machines. As more work should be done to beat rubbing, this additional work is squandered as it is disseminated as warmth vitality.

Purpose/Hypothesis: The objective of this experiment is to show how a can incline affect friction forces. The velocity in both horizontal and inclined position. Also, to discuss the concept of friction and calculate the coefficient of friction of an object by two methods. My hypothesis is that all the numbers will remain the same and not change even if it is done multiple times.

Procedure/Materials: Materials that are needed for this experiment consist of: a can of a soft drink or item of similar weight, ramp about 1-2 meters long made of wood, grooved trim molding or stiff cardboard, friction block set, plastic protractor(15cm), Spring Scale, and a Tape Measure, (3m). Determining force of kinetic or sliding friction and static friction: 1.

The wooden blocks provided in the kit are too light to give good readings so you need to put some weight on them, such as a full soft drink can. Weigh the plain wood block and the object used on top of the block. Record the combined weight in grams and Newtons in Data Table 1.

2.

Place the ramp board you provided horizontally on a table. If necessary, tape it down at the ends with masking tape to keep if from sliding. See Figure 2.

1.

Begin the experiment by setting the block and its weight on the board with its largest surface in contact with the surface of the board. Connect the block's hook to the 500 g spring scale.

2.

Using the spring scale, slowly pull the block lengthwise along the horizontal board as shown in Figure 2. When the block is moving with constant speed note the force

indicated on the scale and record. This is the approximate kinetic or sliding frictional force. Repeat two more times. 3.

While carefully watching the spring scale, start the block from rest. When the block just starts to move, note the force indicated on the scale and record in Data Table 1. You should notice that this requires more force. This force is approximately equal to the static frictional force. Repeat two more times.

2.

Determining force of kinetic or sliding friction and static friction using a different surface area:

1. 2.

3.

Turn the wood block on its side. Repeat the entire process from Part 1 above three times and record the force of kinetic and static friction for each trial in Data Table 2. Determining force of kinetic or sliding friction and static friction using different surface:

1.

Determine the force of kinetic and static friction for the glass surface and sandpapered surface blocks provided.

2.

To further reinforce these concepts, try steps 1-3 using the blocks provided with at least two flat surfaces around your home such as carpet, rubber, tile, cork, etc. Record your findings in Data Table 3, 4, and 5.

4.

Determining coefficient of static friction using an inclined surface:

1.

Place the plain block with its largest surface in contact on the board while the board is lying flat.

2.

Slowly raise one end of the board until the block just breaks away and starts to slide down. Be very careful to move the plane slowly and smoothly so as to get a precise value of the angle with the horizontal at which the block just breaks away. This is the limiting angle of repose ϴmax. Measure it with a protractor (See Figure 3) and record the result in Data Table 6. You may also want to measure the base and the height of the triangle formed by the board, the support, and the floor or table. The height divided by the length of the base equals the coefficient of static friction.. Measuring the inclined surface angle.

1.

Perform two more trials. These trials should be independent. This means that in each case the plane should be returned to the horizontal, the block placed on it, and the plane carefully moved up until the limiting angle of repose is reached. Record results in Data Table 6. Calculations

1.

Using the mass of the block and the average force of kinetic friction from Data Table 1, calculate the coefficient of kinetic friction from Equation 1: Ffr(k)=μkFNThereforeμk=Ffr(k)/FNFfr(k)=μkFNThereforeμk=Ffr(k)/FN

1.

Using the mass of the block and the average force of kinetic friction from Data Table 2, calculate the coefficient of kinetic friction for the wood block sliding on its side. Record your results and see how it compares with the value of µk obtained from Data Table 1.

2.

From the data in Data Table 3, 4, and 5, compute the coefficient of static friction, µs for the glass surface on wood, the sandpapered surface on wood, and wood on carpet, etc., from each of your three trials. Calculate an average value of µs. Record your results in your own data sheets. Ffr(s)=μs FN

1.

Therefore μs=Ffr(s)/FNFfr(s)=μsFN Therefore μs=Ffr(s)/FN

From the data obtained in Data Table 6 calculate µs for wood on wood from each of your three trials and record in Data Table 6. μs=tanθ=sinθmaxcosθmaxorμs=tanθ=heightbaseμs=tanθ=sinθmaxcosθmaxorμs=tanθ=height base

1.

Calculate an average value of µs. Record your result in Data Table 6.

Data/Results/Discussion: :

DATA TABLE 1: Mass of block: 0.424 Kg Weight 4.24 N Flat Board

Trial 1

Force of Kinetic Friction, N 1.87

Force of Static Friction, N 2.43

Trial 2

1.75

2.43

Trial 3

1.52

2.27

Average

1.71

2.38

DATA TABLE 2: Mass of block: 0.424 Kg Weight 4.24 N Flat Board – Block Sideways

Force of Kinetic Friction, N

Force of Static Friction, N

Trial 1

1.27

1.89

Trial 2

1.38

2.18

Trial 3

1.05

1.89

Average

1.23

1.99

DATA TABLE 3: Surfaces Tried: Glass Surface

Force of Kinetic Friction

Force of Static Friction

Trial 1

0.49

0.11

Trial 2

0.38

0.12

Trial 3

0.62

0.14

Average

0.50

0.12

DATA TABLE 4: Surfaces Tried: Sandpaper

Force of Kinetic Friction

Force of Static Friction

Trial 1

3.15

3.67

Trial 2

3.20

3.49

Trial 3

3.17

3.45

Average

3.17

3.54

DATA TABLE 5: Surfaces Tried:

Force of Kinetic Friction

Wood on Carpet

Force of Static Friction

Trial 1

1.46

1.72

Trial 2

1.62

1.85

Trial 3

1.38

1.74

Average

1.49

1.77

DATA TABLE 6: Height

Base Length

θ max

μs

Trial 1

0.425

0.89

25.64

0.48

Trial 2

0.379

0.92

22.29

0.41

Trial 3

0.457

0.73

32.21

0.63

Average

0.420

0.85

26.71

.51

Calculations:

Example of how the answer was calculated(Average/ weight): 1.71/4.94=0.346 Data Table 2: 1.23/4.24=0.290

Table 3:

0.50 / 4.94= 0.101

Table 4:

3.17 / 4.94 = 0.641

Table 5:

1.49 / 4.94 = 0.301

Data Table 1: 1.71 / 4.24 = 0.346

Questions: 1. How does the coefficient of static friction compare with the coefficient of kinetic friction for the same surfaces and areas? It is actually higher than the coefficient of kinetic friction. It would take more to start it going then to maintain it.

2. Why is it important to reduce friction during the operation of machinery? It is important to reduce friction, because it requires more of everything. More power and force to get things moving. Friction has been known to create heat which can cause issues, but the more power it has most likely means more of a cost. 3. How does grease or oil affect the coefficient of friction? It affects it by the frictions to be moved to the fluids and mainly far from the machinery that is used.

Conclusion: In conclusion, while preforming this experiment there were plenty of errors that were made. I feel that this test demonstrated the imperfection in the way that our reading material isn't right in having us expect that the coefficient of active erosion remains the equivalent. This test demonstrated how it changes from preliminary to preliminary because of the way that the surfaces are always showing signs of change along these lines changing the measure of contact. This is likewise a wellspring of blunder because of the way that we couldn't set up the analysis the very same without fail.I assumed while preforming the experiment that the numbers would most likely come out the same way due to the number being so close to each other. In general, I accept that this analysis demonstrated to us that the coefficient of active rubbing isn't steady and furthermore that it merits retaking information so as to comprehend the idea of the lab and the patterns found in the information. Overall, this lab was exceptional, it has allowed me to understand the ways of friction better than before....