Physics T4: Turning effects of forces

Define the term moment

Product of the force F and the perpendicular distance d from the pivot to the line of action of the force

State the formula for moment

M = F x d

M = Moment

F = Force

d = Perpendicular distance from the pivot to the line of action of the force

State and explain what type of physical quantity moment is

- Vector

- Clockwise or anti-clockwise moment

State the SI unit for moment

Nm

State the principle of moments

When a body is at equilibrium, sum of clockwise moments about a pivot is equal to sum of anti-clockwise moments about the same pivot

State the conditions for equalibrim

- No translational motion —> No resultant forces

- No rotational motion —> No resultant motion

Define the term centre of gravity

Imaginary point where the entire weight of an object seems to act

Define the term stability

Measure of an objects ability to return to its original position

Explain, in terms of moments and centre of gravity, why an object topples over

- Line of action of weight is outside base of object

- Resultant clockwise/anti-clockwise moment that causes the object to topple over

Explain, in terms of moments and centre of gravity, why an object is balanced on its pivot

- Line of action of weight is directly above the pivot

- Object is balancing on its pivot

Explain, in terms of moments and centre of gravity, why an object does not topple over

- Line of action of weight is within base of object

- Resultant clockwise/anti-clockwise moment that causes the object to return to original position