Moments, couples and torques

Question 1

what is the definition of moments

Answer 1

moment is a turning effect of a force and it occurs when forces cause objects to rotate about some pivot.

Moment = Force x perpendicular distance from the pivot

Question 2

what do we do when there are no perpendicular forces ?

Answer 2

we need to find the component of D that is perpendicular to F

Question 3

what is the principle of moments

Answer 3

for a system to be in equilibrium, the sum of anti clock wise moments must equal the sum of clock wise moments about the same point

there will be no net force acting on the object ( no net moment)

Question 4

what is a couple ?

Answer 4

a couple is a pair of equal and opposite coplanar forces that acts to produce rotation only.

Question 5

what characteristics should couples have ?

Answer 5

1. equal in magnitude.
2. opposite in direction.
3. perpendicular to the distance between them.