Lab 3 Static Friction mine

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Northern Virginia Community College *

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100

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Physics

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Apr 3, 2024

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docx

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Static Friction Name_Fajar Alim This Lab uses your phone (or an ipad) and an App called Phyphox. An alternative option is given for students who do not have the smartphone. Introduction Frictional forces between two solids arise from the interlocking between the two contact surfaces. The resistance to the motion (friction) typically is proportional to the force that pressures the two surfaces together and to the materials themself. This pressure force is perpendicular to the surfaces and it is called normal force N. Imagine placing a block on a flat surface, like the floor for example, the normal force is the floor support force of the block against the pull down of the force of gravity. The normal force in this case is balancing the weight mg of the block and it is equal to the weight of the block. On an inclined plane, instead the supporting force N is less than the weight mg of the block and the block could slide down pulled by the force of gravity, precisely pulled by the component of the force of gravity along the inclined plane. Friction =( roughness betweenthetwointeractingmaterials ) × ( normal force ) f friction =( coefficient of friction ) ×N = μN Static friction is present when there is no motion of the objects and kinetic friction when there is a relative motion between the two objects surfaces. If you want to go more in depth, for a detailed derivation of the coefficient μ using the formulae for weight and normal force, you may watch this 6.40 minutes video Introductory static friction on an incline by Flipping Physics. In this activity, you will use a method to find the coefficient of static friction between two surfaces. You will place a small object over a flat surface like a large book or a laptop, then slowly you will incline the flat surface until the small object starts to slide. You will record the angle of inclination using the phone. 1/8

If we call the angle that the inclined plane forms with the horizontal, the coefficient of 𝜭 friction μ (pronunciation "mu") is equal to the tangent of the angle . 𝜭 μ = tan ( θ ) (Eq. 1) Activity For a better understanding of the steps, please watch the video called Statics Friction Material needed Any flat object (board, large book, your laptop). You will also use three objects that have a flat side. You will put these objects on the incline and should ultimately slide downhill rather than roll downhill. These objects need to be made of different materials. Examples: an eraser, a small paper box, a game card, a small metal box. In addition, in order to measure the angle of inclination you will use the smartphone and the App Phyphox. Starting hypothesis (2pt) Using your experience, rank the three objects coefficients of friction from the highest (more friction) to the lowest (less friction). Write here your hypothesis. 2/8 Object about to slide down the plane Force of gravity Force of friction ? ? Normal force Force of gravity parallel to the surface Force of gravity perpendicular to the surface

[Answer] If the glasses cover has the highest friction, then the angle of inclination will be lower. The glasses cover will have the most friction, second will be the cards box and the pipe basket will have the least friction. Conduct the experiment 1. Place the flat object on a flat horizontal surface like the floor or a table. Let us say that you are using a large book with a hardcover as a flat object. 2. On the book, place one of the three small objects you will be using to determine the coefficient of static friction and place also the phone. Please check our video explanation. 3. On the Phyphox App select "Inclination". 4. Maintain the first option " Flat tab" and start running the data collection. You will read the values on the "Tilt up/down" plot. 5. Very slowly raise one end of the book up until the object just starts to slide down the incline. At the same time, hold the phone on the surface with your hand. 6. The phone screen will display the increasing angle of inclination. 7. Stop the data collection and tap on the screen. 8. From the bottom of the screen select "Pan and Zoom" and then "Pick Data". 9. Pick the angle that is the largest value during the inclination interval. 10.For each trial, take a screenshot of your smartphone with the point selected and include it at the end of the report. You should have a total of 9 screenshots at the end of your report. 11. Report this angle on the table below in the "Results" section and calculate the value of μ using the Eq. 1. 12.Repeat the same steps for two more trials and report the values of the angles and of the coefficients of static friction on the tables in the "Results" section. 3/8

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