Forces, Moments, and Pressure

Vocabulary flashcards covering turning effects of forces, calculating moments, balance conditions, and pressure concepts based on the provided physics notes.

Lever

An object that turns around a point when a force acts upon it, such as a door handle, bicycle crank arm, or human arm.

Pivot

The point around which a lever turns.

Moment of a force

A physics quantity that describes the turning effect of a force, depending on the size of the force and the distance between the pivot and where the force acts.

Equation for moment

The formula used to calculate turning effect, given by $\text{moment} = \text{force} \times \text{distance}$.

Newton metre ($\text{Nm}$)

The standard unit of moment, written with an upper case N and a lower case m, obtained when force is in newtons ($\text{N}$) and distance is in metres ($\text{m}$).

Door opening moment example

A pulling force of $35\,\text{N}$ applied at a distance of $0.8\,\text{m}$ from the door hinges (pivot) produces a moment of $28\,\text{Nm}$.

Arm weight moment example

A force of $20\,\text{N}$ at a distance of $0.25\,\text{m}$ from the elbow pivot creates a moment of $5\,\text{Nm}$.

Balanced seesaw

A condition achieved when the turning moments on both sides of the pivot are equal and opposite.

Marcus and Arun seesaw example

Marcus weighs $600\,\text{N}$ and sits $2\,\text{m}$ from the pivot ($1200\,\text{Nm}$ moment); to balance the seesaw, Arun who weighs $800\,\text{N}$ must sit at a distance of $1.5\,\text{m}$.

Pressure

The pushing effect of a force, calculated as the force applied divided by the area over which it acts.

Equation for pressure

The mathematical equation given by $\text{pressure} = \frac{\text{force}}{\text{area}}$.

Units of pressure

Units used to measure pressure depending on area, including newtons per metre squared ($\text{N/m}^2$), newtons per centimetre squared ($\text{N/cm}^2$), and newtons per millimetre squared ($\text{N/mm}^2$).

Camel's feet pressure adaptation

Large feet spread the weight of the camel over a large area to decrease pressure on the sand, preventing the camel from sinking.

Drawing pin pressure design

The sharp point has a small area to increase pressure so it easily enters card or wall, while the head end has a large area to decrease pressure so it does not hurt your finger.