Lecture04

# Lecture04 - Sample Problem Friction applied at an angle 1...

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Unformatted text preview: Sample Problem: Friction applied at an angle 1 PHYS 2101, P.M.Shikhaliev LSU, Fall 2010 x y F a x Given: m= 3 kg F = 12 N k = 0.4 Needed: At which angle acceleration will be highest Solution: F net = ma - Newton’s second law F net, x = ma x = F x –f k = Fcos - k F N (1) F net, y = ma y = 0 = F N + F y – F g F N = F g – F y = mg - Fsin (2) Substituting (2) in (1) gives: ma x = Fcos - k (mg - Fsin ) a x = (F/m)cos - k g + ( k F/m)sin a x /d = - (F/m)sin + ( k F/m)cos = 0- sin + k cos = 0 tan = k = 0.4 = 22 o F N F g f k 6.4. The drag force and terminal speed When there is a relative velocity between a fluid and a body (either because the body moves through the fluid or because the fluid moves past the body), the body experiences a drag force, D, that opposes the relative motion and points in the direction in which the fluid flows relative to the body. 2 PHYS 2101, P.M.Shikhaliev LSU, Fall 2010 6.4. Drag force and terminal speed Drag force acts when body moves in fluid or gas. For air, where r is the air density (mass per volume), A is the effective cross- sectional area of the body (the area of a cross section taken perpendicular to the velocity), and C is the drag coefficient . Like friction, it is directed against motion C is unitless because: When a body falls through air, its speed increases, and drag force increases too. At speed v t the drag...
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## This note was uploaded on 09/30/2010 for the course PHYS 2101 taught by Professor Grouptest during the Spring '07 term at LSU.

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Lecture04 - Sample Problem Friction applied at an angle 1...

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