The Principle of Moments Flashcards

All 5 cards in this deck

State the principle of moments.

If an object is balanced, the total clockwise moment about a pivot equals the total anticlockwise moment about that pivot.

What are the steps to find an unknown force acting on a balanced object?

e.g. a $10$ N force acts $0.2$ m to the left of the pivot; force $F$ acts $0.5$ m to the right

1. Find the known moment: $10 \times 0.2 = 2$ N m (anticlockwise)
2. Set clockwise moment = anticlockwise moment: $F \times 0.5 = 2$
3. Rearrange for the unknown: $F = 2 \div 0.5 = 4$ N

True or false? If a seesaw is balanced, the forces on the two sides must be equal.

False. The moments must be equal, so a smaller force further from the pivot can balance a larger force close to it.

True or false? A larger force always produces a larger moment about a pivot.

False. The moment also depends on the perpendicular distance from the pivot.

What happens to an object if the total clockwise moment about its pivot is greater than the total anticlockwise moment?

It is not balanced, so it rotates clockwise about the pivot.