[8] Moments

Question 1

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

Answer 1

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

Question 2

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

Answer 2

Pivot or Fulcrum

Question 3

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

Answer 3

A lever

Question 4

What is the formula for a moment?

Answer 4

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

Units = Newton-metres Or Newton-Centimetres

Question 5

Recite the principle of moments

Answer 5

‘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.’

Question 6

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 _______.

Answer 6

Lever
Effort
Load

Question 7

Where does the weight of a 1 metre ruler act?

Answer 7

At the 50 cm mark

Question 8

Centre of Gravity and Stability

Centre of mass / Centre of gravity definition

Answer 8

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.

Question 9

Lamina definition

Answer 9

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

Question 10

Why does an object topple?

Answer 10

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

Question 11

How can we increase the stability of an object?

Answer 11

Lowering it's centre of gravity
 \_\_\_             —
|  •  | ⬇️ =  |    |
  —            | • |
                   —
Increasing the area of it's base

Question 12

Stable equilibrium definition

Answer 12

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.

Question 13

Unstable equilibrium definition

Answer 13

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.

Question 14

Neutral equilibrium definition

Answer 14

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.

Question 15

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

Answer 15

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