Friction

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Friction is an opposing force that comes into play when one body actually moves or even tries to move over the surface of another body. It acts tangential to the contact surface and opposite to the di…

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When a force is applied on a body at rest, static friction adjusts itself to oppose the applied force. It can be zero if no force is applied, but it becomes nonzero as soon as a force tries to move th…

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Limiting static friction: f_s^{max} = μ_s R Meaning: f_s^{max} is the maximum static frictional force, μ_s is the coefficient of static friction, and R is the normal reaction. Units: f_s^{max} in newt…

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Given: m = 20 kg, F = 98 N, g = 9.8 m/s^2 Since the block is just about to move, F = f_s^{max}. Normal reaction: R = mg = 20 kg × 9.8 m/s^2 = 196 N Step 1: μ_s = f_s^{max} / R = 98 N / 196 N = 0.5 Ste…

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The magnitude of limiting static friction depends on the nature and roughness of the surfaces in contact and not on the size or area of the surfaces. It is directly proportional to the normal reaction…

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The actual contact area is much smaller than the apparent contact area, roughly in the ratio 1:10^4. As the apparent area changes, the microscopic points of actual contact adjust, so friction remains …

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According to modern theory, friction arises from strong atomic or molecular adhesive forces at the points of actual contact. These points form cold welds, and extra force is needed to break them for m…

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Given: m = 2 kg, μ_s = 0.4, applied force F = 2.5 N, g = 9.8 m/s^2 Step 1: Normal reaction R = mg = 2 kg × 9.8 m/s^2 = 19.6 N Step 2: Maximum static friction f_s^{max} = μ_s R = 0.4 × 19.6 N = 7.84 N …