3. Friction - object will slide or move with a uniform...

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Friction and inclined plane Friction force that exists always parallel to the surfaces of bodies in contact force that resists the motion or impending motion of a body force that is always opposite the motion of a body. Two types of friction 1. Static friction (f s ) – the frictional force needed to keep an object from sliding. 2. Kinetic friction (f k ) – the frictional force that exists when the body is in contact with it. Coefficient of friction (μ) - refers to the condition of the surface (roughness or smoothness) F f
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0 < μ < 1 μ = F/N Laws of friction 1. Friction is directly proportional to the normal force. 2. Friction is roughly independent of the velocity or speed of the body. 3. Friction is roughly independent of the surface area in contact. 4. Static friction is always greater than kinetic friction. Angle of repose - also called limiting angle - the angle between a horizontal floor and a plane surface wherein an
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Unformatted text preview: object will slide or move with a uniform velocity (v = k) Problems 1. In the figure, suppose that a block weighs 20N, that the tension P can be increased to 8N before the block starts to slide, and that the force of 4N will keep the block moving at constant speed once it has been set in motion. Find the coefficient of static and kinetic friction. What is the friction force if the block is at rest on the surface and a horizontal force 5N is exerted on it? 2. What force T at an angle 30 o above the horizontal is required to drag a block weighing 20N to the right at a constant speed, if the coefficient of kinetic friction between the block and the surface is 0.20? 3. In the given figure, what must be the value of F so that the block will move up the plane with uniform velocity μ k =0.4. 4. What is the minimum value of A to prevent motion?...
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3. Friction - object will slide or move with a uniform...

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