The Frictional Force and Tension in the String - Lab Report Example

Friction Friction Theory: Friction is a force that always tries to limit the pull or push force when one object is makes contact with another surface. In more simple way, friction is the force that restricts the motion of the one object sliding at another object. Friction is also important in many matters, like cars and vehicles use the friction between tires and roads to move the vehicle. On the other hand, it produces wear and tear in the engine parts when they slide over one another. In order to estimate the friction proper mathematical systems are utilized to evaluate the force of friction between the sliding surfaces. Static friction is the friction that tries to hold the object in position. A book positioned on a table has a static friction. The coefficient of static friction is denoted by µ. Dynamic friction is associated with the surfaces that in constant motion with each other. The friction force between the engine rotating parts is dynamic friction. Objectives: 1. Examine the connection between the usual force, frictional force and coefficient of friction. 2. Evaluate the coefficient of friction for the combination of two materials. 3. Identify the sources of practical errors. Experiment Introduction: The major aim of the experiment is estimate the coefficient of static friction. It can be evaluated by pulling a box with known weight along a surface with smooth flat symmetry. The coefficient of static friction and normal force (FN) are correlated to each other when one surface starts to slide over the surface. FF is the frictional force that is in opposite direction to the tension force. Force of gravity tries to pull the box down and normal pull force (FN) in opposite direction to the gravitational pull force. In this experiment we have to estimate the relationship between FN, FF and µ (coefficient of friction). Apparatus: 1. Two Aluminum Boxes with different weights and surface area (the boxes should have hooks attached to them). One small and one large would be better. 2. Sliding surface (In our case we have a base board) 3. Adjustable pulley (attached to the table) 4. Light rope or thread. 5. Tray to hold the weights/ weights hanger. 6. Different set of weight from 1 gram to 100 grams. Method: 1. Take small box and measure the weight and dimensions of the small box and complete table 1. 2. Adjust the pulley in the middle of one side of the base board. 3. Attach the thread with the hook of the box (small) and then run it over the pulley and attach the other end of thread with the weight hanger. 4. Now keep adding the masses with small incrimination until the box moves from its place towards the pulley. 5. Record the total mass on the weight hanger and fill table 2. 6. Repeat the experiment five times by putting the 100 gram weights each time on the box and complete table 2. 7. Repeat the whole experiment by changing the smaller box with the larger box and complete table 2. Results: Friction Box Parameters Base Material Aluminum Mass Base Cross-sectional Area Box (Small) 202.5 g Box (Large) 594.5 g 256 cm3 Table 1 Mass of Box FN Mass Required for Box to Slip Average FF Box (Small) 0.203 kg 2 N 60g 60 g 50 g 56 g 0.56 N 0.309 kg 2.98 N 80 g 80 g 70 g 76.6 g 0.75 N 0.413 kg 4.05 N 100 g 80 g 80 g 86.6 g 0.85 N 0.516 kg 5.06 N 130 g 110 g 130 g 123 g 1.21 N 0.618 kg 6.06 N 170 g 130 g 140 g 146 g 1.43 N Box (Large) 0.595 kg 5.82 N 180 g 160 g 180 g 166.67 g 1.6 N 0.695 kg 6.8 N 190 g 210 g 190 g 196.67 g 1.9 N 0.795 kg 7.78 N 200 g 240 g 230 g 223 g 2.19 N 0.895 kg 8.76 N 260 g 280 g 270 g 270 g 2.65 N 0.995 kg 9.74 N 320 g 330 g 330 g 327 g 3.21 N Table 2 For small box For large box Discussion Friction of the object is directly proportional to the weight of the object; as the weight increase, the force of friction also increases. During the experiment, the box with more weight required more force to be pulled from its position. It means that the weight of the object increases its frictional value. On the other hand, comparatively less force is required pull the small box. This estimate can either be wrong as heavier weights require more force in general. Coefficient of friction also increases as the weight increases. We have estimated the ratio of FF and FN and found that as the weight of an object increases, the coefficient of friction also increases. The other observation is that the surface area of the object in contact with the other surface also influences frictional force on the object. In our experiment, the box with more weight has more surface area in contact with the surface below and thus produced more friction. On the other hand, the object with lighter weight has smaller surface area in contact with the sliding surface and thus has lower frictional force. The errors in the experiments are due to the sudden increases in weights. Like we are not putting weights with incrimination of one gram at a time, the weights are incremented with an incrimination of 10 gram or so. The whole process produces errors in the accuracy of readings. In order to enhance the accuracy make the reading free of errors, weights are incremented with an incrimination of 10 gram weights at first stage, then 5 gram weights for second stage and one gram weights for third stage. In order to eliminate all the expected errors, it is necessary to clean both the sliding surfaces. Each of the boxes as well as the table should be cleaned thoroughly before the experiment. Conclusion: Both the frictional force and tension in the string are working in opposite direction. The box does not move until the tension in the string is grates than the frictional force. We can conclude that: Tension in the thread < frictional force = box will not move Tension in the thread > frictional force = box will move Normal force is directly proportional to the frictional force. As the frictional force increase, the normal force also increases. Normal force is the function of weight of the object. As the weight increase the normal force also increases. Read More