Chapter 1: Forces and Motion Knowledge Organiser

Vocabulary flashcards covering interaction pairs, gravitational fields, mass and weight, balanced and unbalanced forces, circular motion, and distance-time graphs from Chapter 1: Forces and Motion.

Newton's Third Law

The principle stating that forces arise from interactions, consisting of the force of X on Y and the force of Y on X.

Interaction pair

A set of forces where each force on an object comes from a mutual interaction with another object, and motion changes if forces from different pairs are unbalanced in magnitude.

Gravitational field

A region where objects with mass experience a force, with field arrows indicating the direction of the force.

Gravitational field strength

The force exerted on $1\,\text{kg}$ in $\text{N/kg}$, determined by the slope of a graph of weight against mass.

Mass

A measure of how much 'stuff' is in an object (where an object with more atoms has more mass), which produces a gravitational field.

Weight

The force acting on an object due to gravity, which changes if the gravitational field changes.

Objects in equilibrium

Objects on which the forces are balanced, meaning they will either stay still or go at a constant speed.

Unbalanced forces

Forces that are not equal in magnitude, causing an object to change either its speed or its direction.

Centripetal force

A force acting at $90^\circ$ to the velocity (speed + direction) of an object moving in a circle, changing its direction of motion.

Average speed

The rate of motion calculated by dividing distance by time, typically about $1.5\,\text{m/s}$ for walking and $3\,\text{m/s}$ for running.

Gradient (distance-time graph)

The steepness or slope of a line on a distance-time graph, which gives the speed of the object.

Curved section (distance-time graph)

A section of a distance-time graph that indicates acceleration, where a change from a shallow slope to a steeper slope shows increasing speed.