IGCSE Physics: Forces and Their Effects

Comprehensive practice flashcards covering forces, Newton's laws, Hooke's law, circular motion, friction, and moments based on the IGCSE Physics lecture notes.

Force

Any push or pull on an object due to interaction with another object; it is a vector quantity with the SI unit Newton ($N$).

Resultant Force

A single force, sometimes called the net force, that describes the combined action of all forces operating on a body.

Balanced Forces

Forces that combine in such a way that they cancel each other out, resulting in no resultant force acting on the body.

Unbalanced Forces

Forces that combine in such a way that they do not cancel out completely, producing a resultant force on the object.

Free Body Diagram

A model used to represent forces acting on an object, where each force is shown as a vector arrow scaled to magnitude, pointing in the direction of action, and labeled by name.

Newton’s First Law of Motion

The law stating that objects will remain at rest or move with a constant velocity unless acted on by a resultant force.

Newton’s Second Law of Motion

The law stating that the acceleration of an object is proportional to the resultant force acting on it and inversely proportional to the object's mass.

Newton’s Second Law Formula

$F = ma$, where $F$ is the resultant force ($N$), $m$ is mass ($kg$), and $a$ is acceleration ($m \times s^{-2}$).

Hooke's Law

The principle stating that the extension of a spring is proportional to the applied force, applicable to the initial linear part of a force-extension graph.

Limit of Proportionality

The point past which an object will no longer obey Hooke's law and will not return to its original length; also called the elastic limit.

Fiducial Marker (Pointer)

An instrument used in extension experiments to accurately read the position of the spring from the ruler.

Spring Constant ($k$)

The force per unit extension ($k = \frac{F}{x}$), which serves as a measure of how stiff a spring is, measured in units such as $N/m$, $N/cm$, or $N/mm$.

Circular Motion

Motion along a circular path where an object travels at a constant speed but has a changing velocity because its direction is always changing.

Centripetal Force Requirement

A force acting at $90$ degrees to an object's direction of travel that causes the object to change direction and move in a circle.

Friction

A force between two surfaces that works in opposition to motion, impeding motion and producing heating by transferring energy into thermal energy.

Drag

A type of friction that acts on objects moving through fluids (gases and liquids) due to collisions between the object and fluid particles.

Moment

The turning effect of a force about a pivot, acting in either a clockwise or anticlockwise direction.

Moment Calculation

$\text{moment} = \text{force} \times \text{perpendicular distance}$.

Principle of Moments

The rule stating that if an object is balanced, the total clockwise moment about a pivot equals the total anticlockwise moment about that pivot.

Equilibrium

Conditions met when the forces on an object are balanced (no resultant force) and the sum of clockwise moments equals the sum of anticlockwise moments (no resultant moment).

Centre of Gravity

The point at which the weight of an object may be considered to act.

Plane Lamina

A flat, two-dimensional shape used in experiments to find the centre of mass by tracing plumbline intersections from different pivot holes.

Stability

A property determined by the centre of gravity; an object is most stable when it has a wide base and a low centre of gravity.