6.3 The principle of moments

Question 1

What is the moment of a force about any point?

Answer 1

» Defined as the force x perpendicular distance from the line of action of the force to the point

Question 2

What is the unit of the moment of a force?

Answer 2

» Newtown meter
» Nm

Question 3

What is the equation of the moment of the Force?

Answer 3

» Moment of the force = Force x distance

Question 4

What is the distance d?

Answer 4

» The perpendicular distance from the line of action of the force to the point

Question 5

What is the principle of moments?

Answer 5

» The sum of the clockwise moments = The sum of the anticlockwise moments

Question 6

What is one quick tip when there are several unknown forces?

Answer 6

» Take moments about a point through which one of the unknown forces act
» This point the pivot, will give the force which acts through it a moment of zero, thereby simplifying your calculations

Question 7

What is the centre of mass?

Answer 7

» Is the point through white a single force on the body has no turning effect

Question 8

How do you know if the ruler is uniform?

Answer 8

» If the centre of mass is exactly at the middle of the rule?

Question 9

How can you find the weight of a beam using a known weight and the distance?

Answer 9

» Balance the weight at the end of the pivot, make sure the the beam is off centre, using a knife edge
» The known weight provides anti clock wise distance
» The beam provides a clockwise distance
» Therefore Weight x distance = Weight of beam x distance from the pivot