Science · Grades 7–11
Motion, forces and energy · quick reference
Zero net force means zero acceleration, not necessarily zero velocity. An object can move steadily in equilibrium.
Key terms at a glance
Distance
The total length of the path travelled by an object.
Displacement
The directed change from initial position to final position.
Speed
The rate at which distance is travelled.
Velocity
The rate of change of position, including direction.
Acceleration
The rate of change of velocity.
Net force
The vector sum of all external forces acting on an object.
Inertia
The tendency of an object to resist changes in its velocity.
Friction
A contact interaction that resists relative sliding or attempted sliding between surfaces.
Weight
The gravitational force acting on an object.
Normal force
A contact force perpendicular to the contact surface.
Tension
A pulling force transmitted by a taut string, rope or similar connector.
Kinetic energy
Energy associated with motion.
Gravitational potential energy
Energy associated with position in a gravitational system.
Power
The rate of transferring energy or doing work.
Momentum
The product of an object's mass and its velocity in classical mechanics.
Impulse
The time integral of force, equal to the resulting change in momentum.
Elastic collision
A collision in which total kinetic energy is conserved.
Scalar
A physical quantity described by magnitude without direction.
Vector
A physical quantity described by magnitude and direction.
Equilibrium
A state in which net force is zero; rotational equilibrium also requires zero net torque.
Further reading and review references
These are reference links, not copied exercises, institutional endorsement or proof of independent review.
Learning preview · teacher review required. Grade bands are approximate, not official curriculum alignment.