Matric Phys Definitions

Question 1

Distance

Answer 1

he length of path travelled

Question 2

Displacement

Answer 2

a change in position

Question 3

speed

Answer 3

the rate of change of distance

Question 4

velocity

Answer 4

the rate of change of position or the rate of displacement

Question 5

acceleration

Answer 5

rate of change of velocity

Question 6

Vector

Answer 6

a physical quantity that has both magnitude and direction

Question 7

scalar

Answer 7

a physical quantity that has magnitude only

Question 8

Resultant Force

Answer 8

the single vector (force) which has the same effect as the original vectors (forces) acting together

Question 9

weight

Answer 9

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

Question 10

Normal force

Answer 10

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

Question 11

frictional force

Answer 11

the force that opposes the motion of an object and acts parallel to the surface with which the object is in contact

Question 12

inertia

Answer 12

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

Question 13

Newtons third law

Answer 13

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

Question 14

Potential difference

Answer 14

the work done per unit positive charge

Question 15

current

Answer 15

the rate of flow of charge

Question 16

Ohms Law

Answer 16

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

Question 17

Resistance

Answer 17

a material’s opposition to the flow of electric current

Question 18

Work done on an object by a force

Answer 18

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

Question 19

Gravitational potential energy

Answer 19

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

Question 20

Kinetic energy

Answer 20

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

Question 21

Mechanical energy

Answer 21

the sum of gravitational potential and kinetic energy at a point

Question 22

emf

Answer 22

the total energy supplied per coulomb of charge by the cell

Question 23

Law of conservation of energy

Answer 23

the total energy in a system cannot be created nor destroyed; only transformed from one form to another

Question 24

Principle of conservation of mechanical energy

Answer 24

In the absence of air resistance or any external forces, the mechanical energy of an object is constant

Question 25

Work-energy theorem

Answer 25

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

Question 26

Power

Answer 26

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

Question 27

Watt

Answer 27

the power when one joule of work is done in one second.

Question 28

Efficiency

Answer 28

the ratio of output power to input power

Question 29

Newtons 1st law

Answer 29

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.

Question 30

Newtons 2nd Law

Answer 30

When a net force, Fnet, is applied to an object of mass, 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.

Question 31

Linear momentum

Answer 31

the product of the mass and velocity of the object

Question 32

State Newton's second law in terms of momentum:

Answer 32

The net force acting on an object is equal to the rate of change of momentum.

Question 33

State the law of conservation of linear momentum:

Answer 33

The total linear momentum of an isolated system remains constant

Question 34

Elastic collsion

Answer 34

a collision in which both momentum and kinetic energy are conserved

Question 35

inelastic collision

Answer 35

a collision in which only momentum is conserved

Question 36

Impulse

Answer 36

the product of the net force and the contact time

Question 37

Magnetic flux linkage

Answer 37

the product of the number of turns on the coil and the flux through the coil (NФ)

Question 38

Faraday's law of electromagnetic induction:

Answer 38

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

Question 39

Lenz law

Answer 39

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

Question 40

Diode

Answer 40

a component that only allows current to flow in one direction

Question 41

Define threshold (cut-off) frequency (fo)

Answer 41

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

Question 42

Define work function (Wo)

Answer 42

as the minimum amount of energy needed to emit an electron from the surface of a metal and know that the work function is material specific

Question 43

State Newton's Law of Universal Gravitation:

Answer 43

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

Question 44

Define weight (Fg)

Answer 44

as the gravitational force the Earth exerts on any object on or near its surface

Question 45

Define gravitational field

Answer 45

as the force acting per unit mass

Question 46

State Coulomb's law in words:

Answer 46

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

Question 47

force per unit positive charge E =F/q

Answer 47

where E and F are vectors