4 - Forces in Action Flashcards
Archimedes’ Principle
The upwards force acting on an object submerged in a fluid is equal to the weight of the fluid it displaces.
Centre of Gravity
The single point through which the object’s weight can be said to act.
Centre of Mass
The single point through which all the mass of an object can be said to act.
Couple
Two equal and opposite parallel forces that act on an object through different lines of action. It causes rotation without translation.
Density
The mass per unit volume of a material.
Drag
The frictional force that an object experiences when moving through a fluid.
Equilibrium
For an object to be in equilibrium, both the resultant force and resultant moment must be zero.
Free-Body Diagram
A diagram showing all the forces acting on an object.
Friction
The resistive force produced when there is relative movement between two surfaces.
Moment of Force
The product of a force and the perpendicular distance from the line of action of the force to the pivot.
Newton
The unit of force.
Newton’s Second Law
The sum of the forces acting on an object is equal to the rate of change of momentum of the object.
Normal Contact Force
The reaction force between an object and surface.
Pressure
The force that a surface experiences per unit area. Measured in Pascals (Pa).
Principle of Moments
For an object to be in equilibrium, the sum of the clockwise moments must equal the sum of the anticlockwise moments.
Tension
The result of two forces acting on an object in opposite, outward directions.
Terminal Velocity
The maximum velocity of an object when the resistive and driving forces acting on the object are equal.
Triangle of Forces
A method for determining the resultant force of two forces by joining them tip to tail.
Upthrust
The upwards force that a fluid applies on an object.
Weight
The product of an object’s mass and the gravitational field strength at its location.
