Linear motion
Linear motion is movement along a straight path. Its position changes over time and can be described by displacement, velocity, and acceleration.
Position: Position specifies an object's location relative to a chosen reference frame. Linear motion tracks how this location changes along a straight path.
Kinematics: Kinematics describes motion through position, velocity, and acceleration without explaining its causes. Linear motion is its one-dimensional setting.
Free fall: Free fall is motion under gravity alone, neglecting other forces such as air resistance. Near Earth's surface, it is commonly modeled as uniformly accelerated linear motion.
Rotational motion: Rotational motion is movement around an axis, with points tracing circular paths. It differs from translation along a straight path.
Newton's laws of motion: Newton's laws describe how forces relate to changes in motion and momentum. They explain the forces behind acceleration along a straight path.
Displacement: Displacement is the change in position, including direction, between two points. It gives the net change along the line of motion.
Uniform motion: Uniform motion is motion at constant velocity, with equal displacements in equal time intervals. It is the simplest straight-path case, requiring no acceleration.
Projectile motion: Projectile motion is two-dimensional motion under gravity after an object is launched. Its horizontal component is linear even though the full path curves.
Circular motion: Circular motion is movement along a circular path around a center or axis. Its direction changes continuously, unlike motion on a straight path.
Newton's first law: Newton's first law states that an object's velocity remains constant unless a net external force acts on it. It predicts uniform linear motion when the net force is zero.