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Forces in Static Situations/Lesson Document: Difference between revisions
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A force can rise in two ways: | A force can rise in two ways: | ||
(a) Through contact with another object. Examples:<br /> | (a) Through contact with another object. Examples:<br /> | ||
[[image:FFS1.jpeg| | [[image:FFS1.jpeg|800x1000px]] | ||
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(b) ‘Mysterious’ forces | (b) ‘Mysterious’ forces | ||
These are non-contact forces that occur when objects interact gravitationally or magnetically. There are also ‘mysterious’ electrical no-contact forces.<br /> | These are non-contact forces that occur when objects interact gravitationally or magnetically. There are also ‘mysterious’ electrical no-contact forces.<br /> | ||
[[image:FFS2.jpeg| | [[image:FFS2.jpeg|800x1000px]] | ||
It is quite legitimate to refer to these ‘non-contact’ forces as ‘mysterious’, since even scientists find it difficult to explain how they arise. | It is quite legitimate to refer to these ‘non-contact’ forces as ‘mysterious’, since even scientists find it difficult to explain how they arise. | ||
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"'How do you describe a force?"' | "'How do you describe a force?"' | ||
A force is described in terms of two qualities: its size and its direction. Scientists often use an arrow to indicate the size and direction of a force:<br /> | A force is described in terms of two qualities: its size and its direction. Scientists often use an arrow to indicate the size and direction of a force:<br /> | ||
[[image:FSS3.jpeg| | [[image:FSS3.jpeg|800x1000px]] | ||
'''Where do forces act?'''<br /> | '''Where do forces act?'''<br /> | ||
[[image:FSS4.jpeg| | [[image:FSS4.jpeg|800x1000px]] | ||
The force of reaction acts over a whole surface of contact – it is usually drawn at the centre of the surface, slightly displaced from other ‘force arrows’ for clarity. The two surfaces are also drawn slightly apart for the same reason.<br /> | The force of reaction acts over a whole surface of contact – it is usually drawn at the centre of the surface, slightly displaced from other ‘force arrows’ for clarity. The two surfaces are also drawn slightly apart for the same reason.<br /> | ||
[[image:FSS5.jpeg| | [[image:FSS5.jpeg|800x1000px]] | ||
'''Balanced forces'''<br /> | '''Balanced forces'''<br /> | ||
A stationary object remains still because all the forces acting upon it are ‘balanced’, i.e. the effect of each force acting on a body is cancelled out by an equal and opposite force. When the forces on an object are balanced, a scientist would say there is no net force or no resultant force acting on it i.e. all the forces cancel each other out.<br /> | A stationary object remains still because all the forces acting upon it are ‘balanced’, i.e. the effect of each force acting on a body is cancelled out by an equal and opposite force. When the forces on an object are balanced, a scientist would say there is no net force or no resultant force acting on it i.e. all the forces cancel each other out.<br /> | ||
[[image:FSS6.jpeg|800x1000px]] | [[image:FSS6.jpeg|800x1000px]] | ||
