# Physics P3 2.3 Moments in balance.

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What does the sum of the anticlockwise moments about any point for an object in equilibrium equal?
The sum of the clockwise moments about that point.
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What calculation do we use to calculate the force needed to stop an object turning?
The sum of the anticlockwise moments about any point = the sum of the clockwise moments about that point.
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What is an object if it is balanced?
It is in equilibrium and not turning. We can take the moments about any point and will find that the total clockwise moment and the total anticlockwise moment are equal. This is the principle of moments.
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Seesaws and balance scales are everyday examples of what?
The principle of moments.
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If someone sits in the centre of a seesaw, the moment about the pivot is zero, why?
Because their perpendicular distance to the pivot is zero.
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Aimie sits 2m from the centre of a seesaw. Leo weighs twice as much as Aimie. How far from the centre must he sit to balance the seesaw?
1 m.
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**IN CALCULATIONS BE CAREFUL WITH UNITS. IF ALL THE DISTANCES ARE GIVEN IN CENTIMETRES, THE UNIT OF MOMENT WILL NE THE NEWTON-CENTIMETRE**
**BE SURE TO ADD TOGETHER ALL THE CLOCKWISE MOMENTS AND ALL THE ANTICLOCKWISE MOMENTS, IT MAY HELP TO TICK THEM OFF IF THEY ARE ON A DIAGRAM SO YOU DO NOT MISS ANY OUT**
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## Other cards in this set

### Card 2

#### Front

What calculation do we use to calculate the force needed to stop an object turning?

#### Back

The sum of the anticlockwise moments about any point = the sum of the clockwise moments about that point.

### Card 3

#### Front

What is an object if it is balanced?

### Card 4

#### Front

Seesaws and balance scales are everyday examples of what?

### Card 5

#### Front

If someone sits in the centre of a seesaw, the moment about the pivot is zero, why?