Definitions Glossary — Kinematics — Notes

Term	Symbol	Definition	SI Unit
Distance	d	Total length of path travelled, always positive	m
Displacement	s or $\Delta r$	Straight-line vector from initial to final position; can be negative	m
Speed	—	Distance per unit time; scalar	m/s
Velocity	v	Displacement per unit time; vector	m/s
Acceleration	a	Rate of change of velocity; vector	m/ $s^{2}$
Uniform motion	—	Constant velocity (zero acceleration)	—
Uniformly accelerated motion	—	Constant non-zero acceleration	—
Free fall	—	Motion under gravity alone (a = g = 9.8 m/ $s^{2}$ downward)	—
Projectile	—	Object launched with initial velocity and subject only to gravity	—
Time of flight	T	Total time projectile is in the air	s
Maximum height	H	Highest point above launch level in projectile motion	m
Range	R	Horizontal distance from launch to landing (same level)	m
Angular velocity	ω	Rate of change of angle; ω = v/r	rad/s
Centripetal acceleration	$a_c$	Acceleration directed toward centre of circular path; $a_c = v²/r$	m/ $s^{2}$
Instantaneous velocity	v(t)	Velocity at a specific instant; slope of x-t graph	m/s
Average velocity	$\bar{v}$	Total displacement ÷ total time	m/s
Scalar	—	Physical quantity with magnitude only	varies
Vector	—	Physical quantity with magnitude and direction	varies
Dot product	A·B	$AB\cos\theta$ ; gives scalar	varies
Cross product	A×B	$AB\sin\theta$ ; gives vector perpendicular to both	varies
Relative velocity	$v_{rel}$	Velocity of one object as observed from another	m/s