#### Transcript of Moments and Stability

**Moments and Stability**

Clarence Leung, Malcolm Wong, Ketchup Lee

**Physics - Mechanics**

Moment / Turning Effect of a Force

- Moment of Force:

Force x Perpendicular Distance (from where force is exerted)

- Measured in Newton Metre

Centre of Mass / Gravity

- Geometric property of any object

- The point at which the whole weight appears to act for any orientation of the object

- The centre of an object, where the line of action is a vertical straight line drawn from the centre of gravity, downwards towards the surface

Principle of Moment 1

-Clockwise moment > Anti-clockwise moment, then the object will turn clockwise

Principle of Moment 2

Anti-clockwise moment > Clockwise moment, then the object will turn anti-clockwise

Principle of Moment 3

Clockwise moment = Anti-Clockwise moment, then the object will stay where it is

Rule: If clockwise moment = anti-clockwise moment, the body is in stable equilibrium

When the object is suspended from a point it will come to rest when the clockwise moment is equal to the anti-clockwise moment

Regular and Uniform Objects

Triangle

Externall CoG

Stability

Stability

- A body will be stable as long as the line of action maintains itself inside the base

- If not, then there will be a resultant moment and the body will tend to topple, which makes the object unstable, when the Centre of Gravity falls out of the object’s base

Balancing and Equilibrium

If an object is in equilibrium, then if a force is applied to the object it will either tilt, tip over or roll.

These three conditions are known as:

a) stable equilibrium

b) unstable equilibrium

c) neutral equilibrium

What factors make a modern racing car as stable as possible?

Real Life Situation

Calculate the weight of the beam, W0 if it is balanced when:

W1 = 6N;

d1 = 12 cm;

d0 = 36 cm.

Practice 1

A uniform meter rod of weight 100 N carries a weight of 40 N and 60 N suspended from 20 cm and 90 cm mark respectively. Where will you provide a knife edge to balance the meter scale?

Practice 2

EXAMPLES 1

A 5 m uniform plank weighing 600 N is placed on a level road. A man applies a force at one end. What is the minimum force required to lift it up?

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