Presentation on theme: "Resultant of two forces"— Presentation transcript:
1 Resultant of two forces Learning objectivesResultant of parallel forcesResultant of perpendicular forcesResultant two forces at any angle
2 Resultant of two forces A resultant force is a single force which can replace a set of forces acting on an object. It has exactly the same effect on the object as the original set.Parallel forces7 N4 NResultant force = = 11 N5 N12 NResultant force = = 7 N
4 Two forces at any angle a2 = b2 + c2 – 2b c cos A Resultant R5 N8 N5 N30015003008 NUsing cosine rule :a2 = b2 + c2 – 2b c cos AR2 = – 28 5 cos 150R = 12.6 NUse sine rule to find :Giving: sin = = 11.50
5 Example a2 = b2 + c2 – 2b c cos A Using cosine rule : 130°15 N25 N15 NResultant50°130°25 NUsing cosine rule :a2 = b2 + c2 – 2b c cos AR2 = – 225 15 cos 50R = 19.2 NUse sine rule to find :Giving: sin = = 36.8°
6 ExampleFind the magnitude of the resultant of the forces shown in the sketch, and the angle it make with the larger force.8 N5005 N5 NResultant130°50°8 NBy the cosine rule :R2 = – 2 x 8 x 5 x cos 1300Gives R = 11.9 NBy the sine rule :Gives = 18.80
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