Turning effects of forces
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what is moment or torque?
the turning effect of a force
what is the moment of a force of torque?
the product of the force and the perpendicular distance from the pivot to the line of action of the force
how to calculate moment?
F (force in N) x d (perpendicular distance btw pivot and line of action of force in m)
what is meant by principle of moments?
when a body is in equilibrium, the sum of CW moments about a pivot is equal to the sum of ACW moments about the same pivot.
what is meant when a body is in equilibrium?
the resultant/net force on the body is zero and the resultant/net moment on the body is zero.
define centre of gravity
the point through which its weight appears to act; aka centre of mass
where is the centre of gravity for objects with regular shapes and uniform density?
geometrical centre
what happens to a tilted object at stable equilibrium?
it will return to its original position
where is the line of action through its weight if at stable equilibrium?
it falls within the base
what happens to the centre of gravity when tilted when at stable equilibrium?
it will be raised
what effect does stable equilibrium have on the moment of its weight about the contact point ?
it causes the object to return to its original position
what happens to a tilted object at unstable equilibrium?
it will topple
where is the line of action through its weight if at unstable equilibrium?
it falls outside the base
what happens to the centre of gravity when tilted when at unstable equilibrium?
it is lowered
what effect does unstable equilibrium have on the moment of its weight about the contact point ?
it causes the object to topple
what will happen to the motion of an object at neutral equilibrium?
it will roll to a new position
where is the line of action for neutral equilibrium
through its weight and point of contact coincide
what effect does neutral equilibrium have on the centre of gravity?
it remains at the same height when the object is pushed.
how can we increase the stability of an object?
• lower the centre of gravity • widen its base area