Physics Definitions A Level

Measurement Techniques

Random errors are uncertainties in measurements made by the observer when taking the measurement.

Systematic errors are errors inherent in the instrument.

A measurement is precise if random errors are avoided.

A measurement is accurate if systematic errors have been taken care of.

Kinematics

Displacement is the distance travelled in a specified direction.

Speed is the distance travelled per unit time.

Velocity is the rate of change of displacement.

Acceleration is the rate of change of velocity per unit time.

Dynamics

Newton's First Law of motion states that a body continues to remain at rest or move with constant velocity, unless an external force acts on it.

Newton's second law of motion states that the rate of change of momentum of a body is directly proportional to the force applied and takes place in the direction of that force.

Newton's third law of motion states that when a body A exerts a force on a body B, the body B exerts an equal but opposite force on body A.

Linear momentum of a body is the product of its mass and velocity.

Principle of conservation of linear momentum states that the total momentum pf a system is constant, if no external force acts on it.

Forces

Weight is the force on a mass in a gravitational field.

Electric force is the force on a charge in an electric field.

Up thrust is the force acting in a body in a fluid.

Friction is the force which opposes the motion of a body on a surface.

Viscous force is the force which opposes motion of a body in a fluid.

Moment of a force about a point is the product of the force and the perpendicular distance from the line of action of the force to that point.

A couple is a pair of equal and opposite force, not in line with one another, providing a turning effect.

Work, Power and Energy

Law of conservation of energy states that energy can neither be created nor destroyed but can be transformed from one form to another.

Work is said to be done when the point of application of a force is in the direction of that force.

Gravitational potential energy is the ability of a mass to do work as a result of its position in a gravitational field.

Elastic potential energy is the energy stored in a stretched or compressed spring.

Internal energy of any object is the sum of all the microscopic kinetic and potential energies of the molecules within the object.

Power is the rate of doing work.

Circular Motion

Angular velocity is the rate if change of angular displacement.

Gravitation

Newton's law of gravitation states that any 2 objects in the universe attract each other with a force directly proportional to the product of their masses and inversely proprotional to the square of their separation.

Gravitational field is the space surrounding a mass in which an attractive force is experienced by another mass.

Gravitational field strength at a point is the gravitational force per unit mass acting at that point.

Gravitational potential at a point is the work done in bringing a unit mass from infinity to that point in a gravitational field.

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