WS5A2 Principle of Moments

The principle of moments states the ____ of clockwise moments about a pivot is equal to the ____ of anticlockwise moments about the ____ pivot.

• sum, sum, different

• product, product, different

• sum, sum, same

• product, product, same

Taking moments about R, the 2 N force gives a _____ moment and the W force gives a _____ moment.

• clockwise, clockwise

• clockwise, anti-clockwise

• anti-clockwise, clockwise

• anti-clockwise, anti-clockwise

From the principle of moments, taking moments about R,

Sum of Clockwise Moments = Sum of Anti-Clockwise Moments

• 2 x 18 = W x 50

• W x 50 = 2 x 18

• 2 x 18 = W x (50 - 18)

• W x (50 - 18) = 2 x 18

Which force (s) gives a clockwise moment about point X? (2 answers)

• S

• W

• 2 N

• T

Which force (s) gives an anti-clockwise moment about point X?

• S

• W

• 2 N

• T

Which force (s) gives an anti-clockwise moment about point Y?

• S

• W

• 2 N

• T

Which force (s) gives a clockwise moment about point Y? (1 answer)

• S

• W

• 2 N

• T

Taking moments about Pivot P, which of the following is correct?

• CW moment = W x 18

  ACW moment = 2 x (50 - 18)

• CW moment = W x (50-18)

  ACW moment = 2 x 18

• CW moment = 2 x (50 - 18)

  ACW moment = W x 18

• CW moment = 2 x 18

  ACW moment = W x (50-18)

Taking moments about Pivot X, which of the following is correct?

• CW Moment = T x 100

• CW Moment = 1.1 x 50 + 2 x 60

• ACW Moment = T x 100

• ACW Moment = 1.1 x 50 + 2 x 60

From the principle of moments, taking moments about X for the metre rule,

Sum of Clockwise Moments = Sum of Anti-Clockwise Moments

• T x 100 + 2 x 60 = W x 50

• T x 100 = W x 50 + 2 x 60

• W x 50 = T x 100 + 2 x 60

• W x 50 + 2 x 60 = T x 100