ch4 - forces Flashcards
what is a resultant force?
the single force that has the same effect as all of the forces acting on an object
resultant force of two forces in the straight line?
. same direction, add
. opposite direction, subtract
resultant force of two forces at right angles
use the traingle law
resultant force of three or more forces
find resultant of straight line forces, then traingle law
. if rf = 0, object in equilibrium
. if object in equilibrium, rf = 0 to find value of one of the forces
what is a component?
the magnitudes of a vector quantity in two perpendicular directions
horizontal component =?
F cos 0
vertical component =?
F sin 0
what is resolving?
the process of spiltting a vecotr into two vectors at right angles
what is a free body force diagram?
a diagram showing all the forces acting on an object (NOT the forces it exerts on other objects)
what is the centre of gravity?
the point where the entire weight of an object appears to act
how do you find the centre of gravity of an irregular object?
. suspend plumb line from pins in different locations on the object
. draw lines down the lines
. point of intersection = centre of gravity
what is the moment of a force?
the moment of a forvce about a point is the product of the force and the perpendicular distance from the line of action for the force to the point
moment depends on:
- magnitude of a force
- perpendicular distance of the force from the pivot
moment = Fd
what are the principle of moments?
the sum of the clockwise moments about a point is equal to the sum of anticlockwise moments about the same point, provided the body is in equilibrium
what is a couple?
a pair of equal and opposite forces that act on an object at different points and produce rotation only
