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Unformatted text preview: Types of forces Free-body Diagrams Contact Forces: Normal force: to contact surface ! N Frictional force: || to contact surface ! f ! f ! ! N Simulation: The Ramp look at forces on box when the incline angle is increased two types of friction: ! f s : static (no slipping) and ! f k : kinetic (slipping) coefficients of friction: s and k o s approximately 25% higher than k o s and k depend on the materials in contact F g : interaction pair = box + Earth f s : interaction pair = box + ramp N: interaction pair = box + ramp f static exists because the box tends to slide down the ramp. When = 0, f s = 0 no tendancy to slide no frictional force Part of the weight is working to push the mass down the ramp: mg parallel Part of the weight keeps the box in contact with the ramp: mg normal o Resolve the weight vector into these components F g = mg = hypotenuse of right triangle with vertex angle = mg parallel = side opposite of = mg sin ! mg normal = side adjacent to = mg cos ! Types of forces Free-body Diagrams Block not accelerating forces are balanced f s = mg sin ! N = mg cos ! As increases mg sin ! increases f s increases max = angle when the box starts to slide ! f s = f s ,max ! f s ! s ! N ! f s ,max = s !...
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