Friction

1.      Lab 7: Modeling Friction Forces

a.      Lab conducted by Mohammed Karim (author), Andrew Martinez, Lynel, and Richard Mendoza.

2.      Objective – There are many objectives for this lab. We conducted five experiments. All of these were done to find data, such as maximum static friction, kinetic friction, static friction of a sloped surface, kinetic friction from sliding a block down an incline, and the acceleration of a two mass system.

3.      Theory/Introduction – Friction is a force that acts perpendicular to normal force. It opposes the Normal force. In this lab, we are tasked with finding different parts of friction. Both when an object is at rest (static friction), and when an object is in motion (kinetic friction). We are going to find friction in five different situations.

4.      Apparatus/Procedure –

a.      Due to there being five parts to this experiment, I will break up this lab with each experiment.

b.      1. Static Friction

                                                                i.     

                                                              ii.     In this part of the lab, the goal is to measure the static friction of the board. We placed a pulley with some weights and measured the weight that would cause the block to move. We then increased the normal force, thus increasing the normal force. After measuring the weight of 5 stacked blocks we plotted that data on a graph (See Figure 7.1). This graph is Force of friction over Normal Force. You can see the data on the left and the graph on the right. We put the graph in terms of a power fit. The slope was 0.416.

c.      2. Kinetic Friction

                                                                i.     

                                                              ii.     This part of the lab is pretty straightforward. We placed a block on the board and pulled on it with a calibrated force sensor. We measured the force emitted. A picture of the force graph can be found. (See Figure 7.2)

d.      3. Static Friction from a Sloped Surface

                                                                i.   Better picture in the next section

                                                              ii.     We placed a block on a board and raised it and measured the highest possible angle that the block wouldn’t move at. It was 23.3 degrees.

e.      4. Kinetic Friction from Sliding a Block Down an Incline

                                                                i.     

                                                              ii.     This part of the lab involved measuring the acceleration of an object down an incline. The angle was 21.5 degrees and the object accelerated at 1.449 m/s^2. The coefficient for kinetic friction was 0.23

f.       5. Predicting the Acceleration of a Two-Mass System

                                                                i.   

  

                                                              ii.     From the previous example, we calculated the expected acceleration with a heavy mass. (See figure 7.3 for worked out calculations)

5.      Data Tables

                                                    Figure 7.1

                                                Figure 7.2

                                               Figure 7.3

6.      Conclusion

a.      We learned how to take into account friction in our lab experiments. We were able to accurately calculate the force of friction. This will lower the margin of error on future experiements.