Net ForceUnbalanced ForcesForce VectorsForce DiagramSlide 5Slide 6Motion from ForceInclined PlaneNet ForceNet ForceUnbalanced ForcesUnbalanced ForcesNewton’s Second Law requires a Newton’s Second Law requires a net forcenet force..•One or more forces act on an objectOne or more forces act on an object•Forces are vectors that can be addedForces are vectors that can be addedAdd all vector forces acting on a object.Add all vector forces acting on a object.•If the sum is zero – equilibrium.If the sum is zero – equilibrium.•If the sum is not zero – net force.If the sum is not zero – net force.Force VectorsForce VectorsForce is a vector.Force is a vector.A block sliding on an inclined plane has forces acting A block sliding on an inclined plane has forces acting on it.on it.We know there is a force of gravity and normal force.We know there is a force of gravity and normal force.mForce DiagramForce DiagramNFDraw the forces acting on Draw the forces acting on the block.the block.The force of gravity points The force of gravity points down with magnitude down with magnitude FFgg==mgmg..The normal force points The normal force points away from the surface of the away from the surface of the inclined plane.inclined plane.mmgFgForce DiagramForce DiagramNFDraw components of the Draw components of the forces so the vectors can be forces so the vectors can be added.added.The coordinates should point The coordinates should point along the surface.along the surface.•The normal force is The normal force is unknownunknown•The motion will be along the The motion will be along the surfacesurfaceThe components of The components of FFgg are are compared to the surface.compared to the surface.mmgFgcosmgsinmgxNet ForceNet ForceNFThe block stays along the plane.The block stays along the plane.•No motion or acceleration away from No motion or acceleration away from the surfacethe surface•No force in that componentNo force in that componentSolve for the normal force:Solve for the normal force:Solve for the net force:Solve for the net force:mmgFgcosmgsinmgsinmgFFgxnetcos0cosmgFmgFFFFNNgyNyMotion from ForceMotion from ForceThe net force causes the block to accelerate.The net force causes the block to accelerate.The amount of acceleration is force divided by mass.The amount of acceleration is force divided by mass.This is a constant acceleration moving the block.This is a constant acceleration moving the block.msingmFa Inclined PlaneInclined PlanePushing a block up an Pushing a block up an incline is easier than incline is easier than lifting.lifting.To get constant velocity To get constant velocity a force equal to the a force equal to the downward acceleration downward acceleration must be applied. must be applied.
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