Physics Definition (Prelims P1)

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Define a vector

a physical quantity that has both magnitude and direction

Define a scalar quantity

a physical quantity that has magnitude only

Define resultant vector

the single vector which has the same effect as the original vectors acting together

Define distance

the length of path travelled

Define displacement

a change in position

Define speed

the rate of change of distance

Define velocity

the rate of change of position or the rate of displacement or the rate of change of displacement

Define acceleration

the rate of change of velocity

Define weight $F_g$

the gravitational force the Earth exerts on any object on or near its surtece

Define normal force, $F_N$

the perpendicular force exerted by a surface on an object in contact with it

Define frictional force, $F_f$

the force that opposes the motion of an object

State Newton's first law

An object continues in a state of rest or uniform (moving with constant) velocity unless it is acted upon by a net or resultant force.

Define inertia

the property of an object that causes it to resist a change in its state of rest or uniform motion.

State Newton's second law

When a net force, $F_{ret}$, is applied to an object of masa, $m$, it accelerates in the direction of the net force. The acceleration, $a$, is directly proportional to the net force and inversely proportional to the mass

State Newton's third law

When object A exerts a force on object B, object B simultaneously exerts an oppositely directed force of equal magnitude an object A

Define linear momentum

the product of the mass and velocity of the object

State Newton's second law in terms of momentum

The net force acting on an object is equal to the rate of change of momentum. (Note: there are two acceptable statements of Law)

State the law of conservation of linear momentum

The total linear momentum of an isolated system remains constant (is conserved).

Define an elastic collision

a collision in which both momentum and kinetic energy are conserved

Define an Inelastic collision

a collision in which only momentum is conserved

Define impulse ($J$)

the product of the net force and the contact time

Define the work done on an object by a force

the product of the displacement and the component of the force parallel to the displacement

Define gravitational potential energy

the energy an object possesses due to its position relative to a reference point

Define kinetic energy

the energy an object has as a result of the object's motion

Define mechanical energy

the sum of gravitational potential and kinetic energy at a point

State the law of conservation of energy

the total energy in a system cannot be created or destroyed, only transformed from one form to another.

State the principle of conservation of mechanical energy

in the absence of eir resistance or any external forces, the mechanical energy of an object is constant

State the work-energy theorem

the work done by a net force on an object is equal to the changs in the kinetic energy of the object

Define power

the rate at which work is done or the rate at which energy is transferred

Define efficiency

the ratio of output power to input power

State Newton's Law of Universal Gravitation

Every particle with mass in the universe attracts every other particle with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centres

Define gravitational field

the force acting per unit mass

State Coulomb's law

Two point charges in free space or air exert forces on each other The force is directly proportional to the product of the charges and inversely proportional to the square of the distance between the charges

Describe an electric field

a region of space in which an electric charge experiences a force The direction of the electric field at a point is the direction that a positive test charge would move if placed at that point

Define the magnitude of the electric field at a point

the force per unit positive charge

Define potential difference

the work done per unit positive charge

Define current

the rate of flow of charge

Define resistance

a material's opposition to the flow of electric current

State Ohm's Law

Current through a conductor is directly proportional to the potential difference across the conductor at constant temperature

Define emf

the totul energy supplied per coulomb of charge by the cell

State what magnetic flux density ($B$) represents

a representation of the magnitude and direction of the magnetic field

Define magnetic flux linkage

the product of the number of tums on the coil and the flux through the coil

State Faraday's law of electromagnetic induction

the emf induced is directly proportional to the rate of change of magnetic flux (flux linkage)

State Lenz's law

the induced current flows in a direction so as to set up a magnetic field to oppose the change in magnetic flux

Define a diode

a component that only allows current to flow in one direction

Define work function ($W_o$)

the minimum amount of energy needed to emit an electron from the surface of a metal

Define threshold (cut-off) frequency ($f_o$)

the minimum frequency of incident radiation at which electrons will be emitted from a particular metal