Chap 5: Turning Effect of Forces Flashcards
What is moment of a force?
The turning effect of a force
Another name for moment?
torque
Formula for moment
M = fd
f = force (n)
d = perpendicular distance from pivot to line of action to force (m)
SI unit of moment
Nm
Is moment a vector or scalar quantity?
vector - direction: clockwise or anticlockwise (depending on force & pivot)
In which scenario(s) is moment not present?
when line of action passes through pivot
Examples of moment
- opening a can with a spoon
- door handles
- opening of doors
etc (anything with pivot and force)
State the principal of moments
when a body is in equilibrium, the sum of clockwise moments equals to sum of anticlockwise moments about the same pivot
Results force and moment when the object is in equilibrium?
resultant force & moment on object is zero
What is the centre of gravity?
an imaginary point where entire weight of object seems to act
How to find C.G. for objects with regular shape and uniformed density?
- below the pivot (point of suspension) when hinged
- at geometrical centre (not necessarily on the body itself)
Define stability
measure of its ability to return to original position
Three types of stability?
- stable equilibrium
- unstable equilibrium
- neutral equilibrium
Define stable equilibrium
object is able to return to position after being slightly displaced (line of action is inside body’s base)
Define unstable equilibrium
object topples after being slightly displaced (line of action outside body’s base)
