Posterous theme by Cory Watilo

1.25

1.25 Starter

31 October 2011

12:12

·         Why doesn't the see-saw balance?

 

Explanation

·         The perpendicular distance from the pivot is the same on each side

·         But the force (weight) on the left is great

·         So the moment (turning force) on the left is greater

·         The see-saw will rotate anticlockwise

 

 

 

1.25

Tuesday, July 06, 2010

3:04 PM

·         1.25 recall and use the principle of moments for a simple system of parallel forces acting in one plane

Principle of Moments

·         When a system is balanced then the anticlockwise moments are equal to the clockwise moments

·         This means that the anticlockwise turning force is equal to the clockwise turning force and the system doesn't move

 

Ma = Mc

Fa x da = Fc x dc

 

Ma = anticlockwise moment (Nm)

Fa = force causing the anticlockwise rotation (N)

da = perpendicular distance of Fa from the pivot (m)

Mc = clockwise moment (Nm)

Fc = force causing the clockwise rotation (N)

dc = perpendicular distance of Fc from the pivot (m)

 

 

 

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