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Flashcards in [8] Moments Deck (15):

How can the moment or turning effect of a force be increased?

By increasing the perpendicular distance from the pivot or by increasing the force applied.


The pivotal point of a moment is often referred to as the ...

Pivot or Fulcrum


What name is given to a device that can turn about a pivot?

A lever


What is the formula for a moment?

Moment of a force = Force x Perpendicular distance from pivot
= F x D

Units = Newton-metres Or Newton-Centimetres


Recite the principle of moments

'When a body is in rotational equilibrium the sum of the clockwise moments about any point equals the sum of the anti-clockwise moments about the same point.'


A _____ is any device that can turn about a pivot. In a working lever a force called the ______ is used to overcome resisting force called the ____. The pivotal point is called the _______.



Where does the weight of a 1 metre ruler act?

At the 50 cm mark


Centre of Gravity and Stability

Centre of mass / Centre of gravity definition

A body behaves as if it's whole weight were concentrated at one point, called its centre of gravity (c.g) or centre of mass, event though the earth attracts every part of it.


Lamina definition

A thin 2D irregular or regular sheet/layer of material


Why does an object topple?

A body topples over when a vertical line through it's centre of gravity falls outside it's base.


How can we increase the stability of an object?

Lowering it's centre of gravity
___ —
| • | ⬇️ = | |
— | • |

Increasing the area of it's base


Stable equilibrium definition

A body is in stable equilibrium if when slightly displaced it returns to it's previous position. A ball at the bottom of a round bottomed dish is an example.


Unstable equilibrium definition

A body is in unstable equilibrium if it moves further away from it's original position when slightly displaced. A ball at the top of an upturned round bottomed dish is an example.


Neutral equilibrium definition

A body is in neutral equilibrium if it stays in it's new position when displaced. A ball moved across a table is an example.


Experiment to find the centre of gravity of an irregular 2D shape.

Suspend the shape using thin threads, record the vertical lines across the shape with pencil. Where the lines intersect is the centre of gravity.