Tamil Nadu HSE First Year Physics key terms

A physical quantity that cannot be derived from any other quantity and is defined independently, such as length, mass, time, electric current, temperature, amount of substance and luminous intensity.

A physical quantity obtained by combining fundamental quantities through multiplication, division or powers, such as speed (length divided by time) or force (mass times acceleration).

The internationally agreed base unit of a quantity in the Systeme International, for example metre for length, kilogram for mass and second for time.

An expression showing which fundamental quantities appear in a derived quantity and with what powers, written in square brackets such as [M L T^-2] for force.

The rule that every term in a valid physical equation must have the same dimensions, which allows equations to be checked and unknown relations to be guessed.

The digits in a measured value that carry reliable information about its precision, including one estimated final digit but excluding leading zeros used only as placeholders.

The smallest measurement an instrument can read directly, found by dividing the value of one main scale division by the number of divisions on the vernier or circular scale.

A reading shown by an instrument when the true value is zero, caused by imperfect alignment of its scales; it must be added or subtracted to correct every measurement.

A measuring instrument with a sliding vernier scale used to measure internal and external diameters and depths of small objects to a least count of usually 0.1 mm.

A precision instrument using a rotating screw and circular scale to measure the thickness or diameter of thin objects, typically with a least count of 0.01 mm.

The difference between a measured value and the true value of a quantity, arising from instrument limits, observer technique or random fluctuations in repeated readings.

The absolute error expressed as a fraction of the accepted value and multiplied by one hundred, giving the accuracy of a measurement as a percentage.

A physical quantity fully described by its magnitude alone, with no direction, such as mass, time, speed, work and temperature.

A physical quantity having both magnitude and direction that obeys the triangle law of addition, such as displacement, velocity, acceleration and force.

The single vector that produces the same effect as two or more vectors acting together, found by the parallelogram or triangle law of vector addition.

The process of splitting a single vector into two perpendicular components, usually along horizontal and vertical directions, whose combined effect equals the original vector.

The change in position of a body, a vector drawn from the initial point to the final point regardless of the path actually followed.

The total length of the actual path travelled by a body, a scalar quantity that is always equal to or greater than the magnitude of displacement.

The rate of change of displacement with time, a vector quantity whose direction is that of the displacement; average velocity uses total displacement over total time.

The rate of change of velocity with time, a vector quantity measured in metre per second squared and directed along the change in velocity.

The two-dimensional motion of a body thrown into the air under gravity alone, combining constant horizontal velocity with uniform vertical acceleration.

The natural tendency of a body to resist any change in its state of rest or uniform motion, measured quantitatively by its mass.

A body continues in its state of rest or uniform motion in a straight line unless acted upon by a net external force; also called the law of inertia.

The net force on a body equals the rate of change of its momentum, which for constant mass reduces to force equals mass times acceleration.

For every action there is an equal and opposite reaction; forces always occur in pairs acting on two different bodies and never cancel on the same body.

The product of a force and the short time for which it acts, equal to the change in momentum produced; it is a vector measured in newton second.

In the absence of external forces, the total momentum of an isolated system of interacting bodies remains constant before and after any collision or explosion.

The contact force that opposes relative motion or the tendency of motion between two surfaces, arising from irregularities and molecular adhesion at the interface.

The product of force and the displacement of the point of application measured along the force, a scalar with the unit joule.

The energy possessed by a body by reason of its motion, equal to half the mass multiplied by the square of its speed.

Energy can neither be created nor destroyed but only transformed from one form to another; the total energy of an isolated system stays constant.

The rate at which work is done or energy is transferred, measured in watt, where one watt equals one joule per second.

The point at which the entire mass of a body or system may be considered concentrated for describing its translational motion under external forces.

A measure of a body's resistance to change in its rotational motion, equal to the sum of each mass element multiplied by the square of its distance from the axis.

The turning effect of a force about an axis, equal to the product of the force and the perpendicular distance from the axis to its line of action.

The rotational analogue of linear momentum, equal to moment of inertia times angular velocity for a rigid body about a fixed axis, conserved when external torque is zero.

The minimum speed with which a body must be projected from a planet's surface to escape its gravitational field and never return, about 11.2 km per second for Earth.

The speed required for a satellite to stay in a circular orbit around a planet, equal to the square root of gravitational parameter divided by orbital radius.

The acceleration produced in a freely falling body by the Earth's gravitational attraction, approximately 9.8 metre per second squared near the surface.

Within the elastic limit, the stress on a material is directly proportional to the strain produced, giving a straight-line stress-strain graph in that region.

The ratio of longitudinal stress to longitudinal strain within the elastic limit, a measure of the stiffness of a solid material.

The greatest stress a material can bear and still return to its original shape and size when the load is removed; beyond it permanent deformation occurs.

The property of a liquid surface behaving like a stretched membrane, caused by unbalanced inward molecular forces, measured as force per unit length.

The internal resistance of a fluid to flow, arising from friction between adjacent layers moving with different speeds; it decreases as temperature rises in liquids.

The heat supplied to a system equals the increase in its internal energy plus the work done by the system on its surroundings.

A change in which no heat is exchanged between the system and its surroundings, so any work done comes from or goes into the internal energy.

A change in which the temperature of the system remains constant throughout, so the internal energy of an ideal gas does not change.

The total kinetic and potential energy of the molecules of a system, a state function that changes with temperature and depends on the amount of substance.

The average distance travelled by a gas molecule between two successive collisions with other molecules, which decreases as pressure rises.

A model explaining gas behaviour by treating molecules as tiny particles in random motion that collide elastically, with pressure arising from collisions with the walls.

The number of independent ways a molecule can store energy, such as three translational modes for a monatomic gas, used to compute specific heats.

A periodic motion in which acceleration is directly proportional to displacement from a fixed mean position and always directed towards it.

The time taken by a body in periodic motion to complete one full oscillation and return to the same position moving in the same direction.

The number of complete oscillations made by a periodic motion in one second, measured in hertz and equal to the reciprocal of the time period.

A large increase in oscillation amplitude when the driving frequency of an external force equals the natural frequency of the oscillating system.

The apparent change in the frequency of a wave observed when the source, the observer, or both move relative to the medium carrying the wave.