Experiment P-6, Friction Force
Contents
1. Force Ver 3 4 4 4 NeuLog EJ sensor setup 5 Connect the USB module va to the PC 6 Connect the force sensor to the USB 200 module Note The following application functions are explained in short It is recommended to practice the NeuLog application functions as described in the user manual beforehand 7 Run the NeuLog application and check that the force sensor is identified Experiment P 6 Friction Force Ver 3 4 4 5 NeuLog EZ settings 10 Click on the On line Experiment icon Ga in the NeuLog main icon bar Click on the Sensor s Module box Click on the Push Negative button to get positive values when pulling the hook NeuLog Al EA 9 its gt o amp Back Expenment Load Erase Run Stop Save pen Setup Experiment Experiment Experiment Experiment Experiment Experiment Force id 1 Duration 10 seconds Rate 10 per second Color Display Y axis Trigger Reset lb Push Positive Grid Graph Table Point Area Experiment P 6 Friction Force Ver 3 4 4 6 NeuLog EZ 11 Click on the Range button 12 Select the 10 N button to change the sensor s mode aS NeuLog 4l EA BE E D amp os Back Experiment Erase Single Run Save Open Setup Experiment Step Experiment Experiment Experiment Force id 1 Range 10 N Color Display Y axis Reset Push Negative Push Positive E H Be Grid Graph Table Point Area m 13 Click on the Experiment setup2. force of friction and the normal force that presses the surfaces together Because it is a force divided by a force u does not have any units Friction force depends on the object s mass part of the normal force however the friction coefficient is not a function of mass it depends only on the properties of the surfaces When an object is at rest the amount of force required to move it is usually greater than the force required to keep it moving Therefore typically there is a difference between the coefficient of static friction before motion starts and the kinetic friction in motion The static friction coefficient u is calculated at the threshold of motion while the kinetic friction coefficient ug is calculated during motion friction force is constant In this experiment we will use a force sensor to study the frictional force of different surfaces and different weights Experiment P 6 Friction Force Ver 3 4 4 3 NeuLog ES Procedure Experiment setup 1 set up the experiment as shown in the picture below P 2 Place a block with one smooth side and one rough side on the table The rough side should be in contact with the table 3 Attach the block to the force sensor s hook with a thread There should be around 10 cm between the block and the force sensor 4 Place the 1 kg mass 1000 g on the block We add weight to the block in order to see the different types of friction forces Experiment P 6 Friction
3. 1 NeuLog EJ Experiment P 6 Friction Force amp Objectives To learn about the relationship between friction force normal force and friction coefficient To observe changes in the friction force within different surfaces and different masses To calculate the friction coefficients static and kinetic in these different conditions Modules and Sensors PC NeuLog application USB 200 module NUL 211 Force logger sensor Equipment and Accessories Rough and smooth wooden block with hook 20 cm of thread 1000 g mass 500 g mass The items above are included in the NeuLog Mechanics kit MEC KIT Experiment P 6 Friction Force Ver 3 4 4 2 NeuLog EJ Introduction Friction force is created when two surfaces move or try to move against each other The direction of the friction force is always opposite to the direction of motion or motion attempt and parallel to the surface therefore it resists the relative motion of the surfaces Friction force depends on the roughness of the surfaces and the normal force which presses the surfaces together It can be described by the following equation F Friction UN Applied force gt Friction force E When the object is on a horizontal surface and there are not any other force components acting on it perpendicular to the surface then the normal force equals the object s weight thus Favicon umg The coefficient of friction u is the ratio between the
4. 4 11 AY 1 310 Open periment ve Experiment Ex o 0 0 5 1 1 5 2 2 5 3 3 5 4 4 5 5 ER 2 Time Second A Q BIA le bes HEV BBL m Unzoom Zoom Zoom Select Line Show Grid Graph Table Point Area All Fit Zone Width Functions Selected area X1 2 04 5 A2 2 26 5 AX 0 22 5 1i 5 42 N Y2 4 44 N AY 1 3140 23 In the sample experiment the friction force at the transition point is 5 42 N In order to calculate the static friction coefficient we should place this value in the following equation Fs max Hsmg Experiment P 6 Friction Force Ver 3 4 4 24 10 NeuLog EZ The friction force at motion is 4 11 N In order to calculate the kinetic friction coefficient we should place this value in the following equation Fk umg In our case the total mass is 1 24 kg therefore mg 1 24 kg x 9 8 m s g gravitational acceleration 12 15 kg x m s 12 15 N To find the friction coefficients we divide each force value by mg total weight Static see Kinetic Surface Ha ee static friction eae friction kg friction coefficie force N coefficie force N nt us nt ug Fill the first row in the following table with your results and calculations If you repeated the measurement use the average values Block s Mass on Max Static Kinetic Kinetic f the block static friction friction friction oE Tk T Tk i friction coefficie force N coefficie L force N nt us Nt uk Experi
5. Open Experiment Experiment a Static friction Kinetic friction Transition point 8 7 6 5 4 3 2 1 0 1 N Before applying force on the bock Q Balg BB BB be Unzoom Zoom Zoom Select Line Show Grid Graph Table Point Area All Fit Zone Width Functions 19 Save your graph 20 The sensor measures the resistance of the block to motion i e the friction force At the beginning of the graph the friction force is zero because the block does not move and there isn t any applied force on it As we apply force on the block by pulling it the block resists and do not move at this part the friction force equals the applied force and is considered static friction The highest possible static friction value is called the transition point We can use this value in order to calculate the static coefficient Fomax Usmg Experiment P 6 Friction Force Ver 3 4 4 9 NeuLog EJ After this point the block starts moving as we pull it the friction force decreases and then becomes constant We can use the friction value at this range to calculate the kinetic friction coefficient Fk umg 21 Itis recommended to repeat every measurement three times el 22 In each graph click on the Select Zone icon and select the part between the transition point static friction force and the other one to the point where the force becomes constant Selected area X1 2 04 5 X2 2 26 5 Back 6s AxX 0 22s Y1 5 42 N Y2
6. icon and set the Experiment duration to 5 seconds Sampling rate to 50 per second Experiment P 6 Friction Force Ver 3 4 4 7 NeuLog ES Testing and measurements Note The orientation of the sensor is very important Before each measurement hold the sensor in the same position you will use for the specific experiment and zero it 14 Sensor Zeroing hold the sensor in its proper position on the table and press the button in the sensor s box for about 3 seconds Alternatively you can click on the Reset button in the Module Setup box menu 15 Click on the Run experiment icon LJ to start the measurement 16 Hold the force sensor on the table and slowly pull the block horizontally while increasing the force the direction should be in a straight line when you reach a certain force the block will start to move keep the block moving at a about the same velocity until the end of the measurement The part in which you increase the applied force should be done in around one second Practice this until you see a relatively smooth motion in your graph Experiment P 6 Friction Force Ver 3 4 4 8 NeuLog EZ 17 If needed click on the Zoom fit icon a or click on the Zoom icon Q and locate the mouse cursor at a point above the graph and press its left button keep it pressed and create a rectangle that includes the whole graph 18 Your graph should be similar to the following NeuLog Al amp amp Back Save
7. ment P 6 Friction Force Ver 3 4 4 11 NeuLog EJ 25 Proceed in this way with the smooth side on the table will the friction force be different Will the friction coefficients be different 26 Fill the second row of the table with your results and calculations 2 Proceed in this way with each side of the block but now put also the 500 g mass on the block 28 Fill the third and forth rows of the table with your results and calculations Experiment P 6 Friction Force Ver 3 4 4 12 NeuLog EJ Summary questions 1 Compare the following values you received If there is a difference between the values explain it a Static vs kinetic friction coefficients in each measurement b Friction coefficients of the rough surface vs the smooth surface with the 1000 g c Friction coefficients of the rough surface with the 1000 g mass vs the same surface with the 1500 g mass 2 Think about what would happen in a world without friction What would happen if you tried to walk What would happen if you slide an object across the ground Experiment P 6 Friction Force Ver 3 4 4
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