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Forces in 2D. Force. A push or pull Vectors – magnitude and direction Newton’s 2 nd law – F = ma Units of Newtons (N) Fnet is the sum total of all the forces acting on an object If Fnet = 0, acceleration = 0 which means either no motion OR constant speed
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Force • A push or pull • Vectors – magnitude and direction • Newton’s 2nd law – F = ma • Units of Newtons (N) • Fnet is the sum total of all the forces acting on an object • If Fnet = 0, acceleration = 0 which means either no motion OR constant speed • If Fnet >0, then there is acceleration • Types of forces – applied, friction, weight (force due to gravity), normal • Ff = FnFn = -FgFg = mg(-9.8m/s2)
Review Problem You push a 25.0 kg wooden box across a wooden floor at a constant speed of 1.0 m/s. How much force do you exert on the box? The coefficient of friction between the box and floor is 0.20. Fn Ff Fapp Fg
Example of 2D A student moves a box of books by attaching a rope to the box and pulling with a force of 90.0 N at an angle of 30.00 to the horizontal. The box of books has a mass of 20.0 kg and the coefficient of kinetic friction between the bottom of the box and the sidewalk is 0.50. Find the acceleration of the box. Fn Fapp Ff 300 Fg