3.4.1.2 - Moments

Question 1

Moment =

Answer 1

force (N) x perpendicular distance from the point to the line of action of the force (m)

Question 2

In equilibrium what must be equal?

Answer 2

cm=acm

Question 3

What is a couple?

Answer 3

A pair of equal but opposite coplanar features.

Question 4

What does a couple cause?

Answer 4

Doesn’t cause any resultant linear force, but does produce a turning effect.

Question 5

Moment of a couple =

Answer 5

force × perpendicular distance between the lines of action of the forces.

Question 6

Weight =

Answer 6

mass x gravitational field strength

Question 7

How do you find the centre of mass experimentally?

Answer 7

1. Hang the object freely from a point.
2. Draw a vertical line downwards from the point of suspension using a plumb bob to get your line exactly vertical.
3. Hang the object from a different point.
4. Draw another vertical line down.
5. The centre of mass is where the two lines cross.

Question 8

What two things does a moment depend on?

Answer 8

• distance from the pivot.

- force applied.

Question 9

What does it mean if a body is in stable equilibrium?

Answer 9

When displaced it will return to its equilibrium position.

Question 10

If in equilibrium Fxd

Answer 10

= Wb/2

Question 11

In order for something to topple?

Answer 11

Fxd > Wb/2

Question 12

What must occur in order for any body to be in equilibrium?

Answer 12

• The resultant force must equal zero.

- The principle of moments must apply.

Question 13

Centre of gravity?

Answer 13

The point where the weight of the object appears to act.