4 Forces Flashcards
Hooke’s Law
Force is directly proportional to the extension/compression in a material if its limit of proportionality is not exceeded
F = kx (where k is force constant of spring)
k(eff) of series spring system
1/k(eff) = 1/k1 + 1/k2 + …
k(eff) of parallel spring system
k(eff) = k1 + k2 + …
Centre of gravity
The point at which the entire weight of a body may be considered to act
Moment of a force
The product of the force and the perpendicular distance of the line of action of the force from the pivot.
Torque of a couple
The products of one of the forces and the perpendicular distance between the lines of action of the forces
Principle of Moments
For a body in equilibrium, the sum of its clockwise moments about any axis is equal to the sum of its anticlockwise moments about the same axis.
Density
The mass per unit volume of a substance.
Pressure
Force per unit area, where the force is acting perpendicularly to the area.
Upthrust
The vertical upward buoyant force when a body is immersed in a fluid.
Archimedes’ Principle
When a body is totally or partially immersed in a fluid, it experiences an upward force (upthrust) equal to the weight of fluid displaced
Principle of Floatation
For an object floating in equilibrium, upthrust is equal to the weight of the object
