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Course: Applied Mathematics — Second Secondary
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Forces

Applied Mathematics — Second Secondary

Forces

Common types of forces

Common types of forces

Type of force Definition Direction
Weight
  • The pull of the Earth on a body
  • equals mass × g
Vertically downwards towards the centre of the Earth
Tension in a string The force transmitted by a taut string to the body attached to it Along the string, pulling away from the body
Normal reaction The force exerted by a surface on a body resting on it Perpendicular to the surface, away from it
Friction A force between two rough surfaces in contact that opposes the motion or the tendency to move Parallel to the surface
  • Weight is a force, not a mass.
  • Mass is a fixed quantity that does not change with place, while weight changes when the value of g changes.
  • The weight is calculated from:
  • Weight W = mass m × g
  • If a body rests on a horizontal surface, the normal reaction has the same magnitude as the weight.
  • In equilibrium problems we draw a force diagram showing all the forces acting on the body as arrows.
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