Module 3 - 3.2.3 Equilibrium

Question 1

Moment (definition)

Answer 1

The moment of a force is the product of a force and the perpendicular distance from the pivot

Question 2

Conditions Needed for Equilibrium

Answer 2

• no net force
• no net moment

Question 3

Principle of Moments

Answer 3

For an object to be in rotational equilibrium the sum of the clockwise moments must equal the sum of the anticlockwise moments (i.e. no net moment)

Question 4

Couples (definition)

Answer 4

A couple consists of two antiparallel (parallel but act in opposite directions) force of equal magnitude with a perpendicular distance between them

Question 5

Torque (3)

Answer 5

• The turning effect of a couple
• One of the forces multiplied by the perpendicular distance between the forces
• Always the same no matter where the pivot is

Question 6

Centre of Mass (definition)

Answer 6

The single point at which the mass of an object appears to act

Question 7

Centre of Gravity (definition)

Answer 7

The single point at which the weight of an object appears to act

Question 8

If a force doesn’t act directly through the object’s centre of mass…

Answer 8

the object will move with an added rotation

Question 9

Stability (2)

Answer 9

• For an object to be stable, its centre of mass must be above its base
• The lower the centre of mass/the wider the base area, the more stable

Question 10

As an object turns from horizontal to vertical the size of it moment

Answer 10

decreases to zero