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P8 Forces in Balance (Vectors and Scalars (A scalar quantity has magnitude…
P8 Forces in Balance
Vectors and Scalars
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A vector quantity can be represented by an arrow in the direction of the vector and of length in proportion to the magnitude of the vector
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Forces Between Objects
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Forces can change the shape of an object, or change its motion or its state of rest
When two objects interact, they always exert equal and opposite forces on each other
Resultant Forces
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If two forces act on an object along the same line, the resultant force is:
Their sum, if the forces act in the same direction
Their difference, if the forces act in opposite direction
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The resultant force is a single force that has the same effect as all the forces acting on an object
Moments at Work
To increase the moment of a force, increase the force or increase the distance
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Levers and Gears
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To increase the moment of a turning effect, a small gear wheel needs to drive a larger gear wheel
The pivot of a force multiplier is nearer to the line of action of the force it exerts than to the force applied to it
A level used as a force multiplier exerts a greater force than the force applied to the lever by the effort
Centre of Mass
When an object is freely suspended, it comes to rest with its centre of mass directly underneath the point of suspension
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Resolution of Forces
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To resolve a force in two perpendicular directions, draw a rectangle with adjacent sides along the 2 directions so that the diagonal represents the force vector
Resolving a force means finding perpendicular components that have a resultant force that is equal to the force
Moments and Equilibrium
The direction of the force and the position of the fixed point determines whether the moment acts clockwise or anticlockwise
All the forces acting on an object that don't pass through a fixed point can turn an object about that point
If an object at rest doesn't turn the sum of the anticlockwise moments about any point = the sum of the clockwise moments at that point
Parallelogram of Forces
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The parallelogram of forces is used to find the resultant of two forces that do not act along the same line
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