Basic Definitions in Physics

Below are some basic definitions in physics that you are likely to need or come across when studying physics at school.

Speed

Speed is the rate of change of distance.

Velocity

The velocity is the rate of change of displacement.

Acceleration

The acceleration is the rate of change of the velocity.

Newton's Laws

1st: Newton's First law states that every body continues in its state of rest or of uniform motion in a straight line unless acted on by some external force.

2nd: Newton's Second Law states that the rate of change of momentum of a body is directly proportional to external force acting on the body and takes place in the direction of the force.

3rd: If a body A exerts a force on a body B, then B exerts an equal and opposite directed force on A.

Linear Momentum

The linear momentum is the product of mass and velocity.

Force

The force is the rate of change of momentum.

Conservation of Momentum

The conservation of Momentum states that the total (linear) momentum of a system of interacting bodies, on which no external forces are acting, remains constant.

Moment of a force

The moment of a force = force x perpendicular distance from the pivot to the line of action of the force.

Torque of a couple

The torque of a couple or pair of equal and opposite parallel forces lines of action do not coincide is the product of one or the forces and perpendicular distance between the lines of action.

Potential at a point

The potential at a point is the workdone in bringing unit mass from infinity to the point.