Turning Effect of Forces Flashcards
What is the equation of moment of force
Moment = Fd (unit: Nm)
Why may there be no resultant moment about a pivot by one force
Zero perpendicular distance from pivot to line of action OR line of action of force passes through the pivot
What is the relationship between pivot and weight of body
If line of action of weight has perpendicular distance from pivot, a moment is generated causing the object to rotate
How is equillibrium achieved
- Resultant force on the object is zero
- Th resultant moment about any point on the object is zero
State the Principle of Moments
For an object in equillibrium, the sum of clockwise moments about any point is equal to the sum of anti-clockwise moments about the same point
Why does the design of a sack truck make it easier to lift a load
For same moment, perpendicular distance from pivot to line of action of effect force provided by hands is larger than perpendicular distance from pivot to line of action of weight of sack. Hence, E will be smaller than W
How to increase the stabiliity of an object
Lower its centre of gravity or increase its base area
Why does the box return to its original position after being tilted slightly on one corner?
This ensures the line of action of weight falls within its base and moment of weight about the pivot returns object to its original position
Why does heavy base make a box more stable
A heavy base lowers the centre of gravity so the box does not tip over
Why can balancing toys rarely tip over
The moments due to hidden weights cause the centre of gravity to be directly below the pivot so weight of an object does not produce a moment about the pivot when balanced as perpendicular distance from line of action of weight to pivot is zero.
Why do objects fall over when tilted beyond a certain point
The line of action of weight will fall outside of the (pivot point) and produces a clockwise/anticlockwise moment about the (pivot point), causing it to fall over
