Physics definitions

Question 1

photon

Answer 1

• a very small quanta of discrete light energy

- can be an electromagnetic wave or particle

Question 2

Absorption spectrum

Answer 2

• a coloured background with black lines

Question 3

Emission spectrum

Answer 3

a black background with coloured lines

Question 4

a moment

Answer 4

the perpendicular distance to the pivot times the force

• forces up equal forces down
• anticlockwise moments equal clockwise moments

Question 5

Equilibrium

Answer 5

an object is in equilibrium when the resultant forces acting on a particle is zero

Question 6

Couples

Answer 6

a pair of forces equal in magnitude and opposite in direction

Question 7

Centre of mass

Answer 7

the point at which your mass acts through

Question 8

Difference between centre of mass and centre of gravity

Answer 8

the gravitational field is not uniform

Question 9

How to improve centre of mass

Answer 9

lower centre of mass

widen base of the object

Question 10

kinetic energy

Answer 10

energy associated with anything that is moving

Question 11

elastic collisions

Answer 11

kinetic energy and momentum is conserved

small scale

Question 12

inelastic collisions

Answer 12

momentum is conserved

large scale

Question 13

Impulse

Answer 13

the rate of change of momentum

Question 14

current

Answer 14

the flow of charge per unit time

Question 15

voltage

Answer 15

how many joules of work each coulomb of charge is capable of doing

Question 16

potential difference

Answer 16

• the energy transfer per unit/ from electrical to other

- charge losing energy

Question 17

Electromotive force

Answer 17

the charge gaining energy

Question 18

resistivity

Answer 18

the resistance a metal puts up to electric current

Question 19

hooke’s law

Answer 19

the force exerted on a spring is proportional to its compression, such that force divided by compression is equal to a constant k, which is measured in Nm

Question 20

thermistor

Answer 20

a device that decreases its resistance as temperature increases

Question 21

Young modulus

Answer 21

the modulus of elasticity

Question 22

Brittle

Answer 22

something which shatters if a large stress is applied

Question 23

Ductile

Answer 23

a material that can be easily shaped under tension

Question 24

Malleable

Answer 24

a material that can be easily shaped under compression

Question 25

Wavelength

Answer 25

the distance between two identical points on successive waves

Question 26

amplitude

Answer 26

the maximum displacement of a wave

Question 27

period

Answer 27

the time taken for one complete wave to pass a point

Question 28

frequency

Answer 28

the number of waves that passes a fixed point per unit time

Question 29

transverse waves

Answer 29

waves that have their displacement at 90 degrees to the direction of energy transfer

Question 30

longitudinal waves

Answer 30

waves that have their displacement in the same direction as the energy transfer

Question 31

phase difference

Answer 31

the amount a wave is in or out of sequence with another wave

Question 32

Coherence

Answer 32

when two waves have a constant phase difference

Question 33

refraction

Answer 33

when a wave travels from a fast medium to a slow medium or vice versa causing waves to slow down and speed up and turn

Question 34

Interference

Answer 34

when two waves meet at a point, the resultant displacements the sum of individual displacements

Question 35

path difference

Answer 35

- if the path difference is even and whole waves, the waves will arrive in phase - if odd the waves will arrive out of phase

Question 36

superconductivity

Answer 36

zero resistance - occurs at low temperature - has no resistance after a certain critical temperature

Question 37

antiparticle

Answer 37

different charge | same mass, rest mass energy

Question 38

hadrons

Answer 38

heavier not fundamental made of fundamental quarks interacts with SNF,WNF and electrostatic if charged

Question 39

leptons

Answer 39

lighter fundamental does not interact with the SNF interacts with WNF and electrostatic force if charged