Phys - Unit 3

Question 1

Relative Atomic Mass

Answer 1

System to measure mass where 1 = the mass of one nucleon

hydrogen has a Mr of 1

Question 2

Unified Atomic Mass Unit

Answer 2

u = 1.66x10^-27 kg = 1Da

Question 3

Molar Mass

Answer 3

System to measure mass where 1mol = number of atoms in 12g of C-12 = 6.02x10^23

Molar mass of C-12 is 12gmol^-1

Question 4

Ideal Gas Assumptions

Answer 4

NISCER

Negligible volume
Intermolecular forces
Straight lines
Constant motion
Elastic collisions
Random distributed energy & motion

Question 5

Relationship between V & p (boyles)

Answer 5

1/V ∝ p

p1V1 = p2V2

Question 6

Relationship between V & T (charlie)

Answer 6

V ∝ T

V1/T1 = V2/T2

Question 7

Relationship between p & T (gay)

Answer 7

p ∝ T

p1/T1 = p2/T2

Question 8

Circular motion velocity and acceleration

Answer 8

a = -(ω^2 x)

v = ω x

Where x = A, the velocity and acceleration are maximum

Question 9

SHM displacement, velocity and acceleration

Answer 9

x = A cos(ωt + ε)

v = -Aω sin(ωt + ε)

a = -Aω^2 cos(ωt + ε)

ε represents the phase of the system

Question 10

Period of a spring and pendulum

Answer 10

Ts = 2π√(m/k)

Tp = 2π√(l/g)

Question 11

Horizontal mass-spring system energy description

Answer 11

1/2 kA^2 = 1/2 mv^2 + 1/2kx^2

Question 12

Pendulum energy description

Answer 12

r - rcos(θmax) = hmax

mghmax = 1/2 mv^2 + mgh

Question 13

pV & Energy Equations

Answer 13

pV = nRT
= NkT
= 1/3 Nmc^2

Ek = 3/2 pV

Question 14

Deriving pV = 1/3 Nmc^2

Answer 14

1. Draw container and label all side lengths & mass and velocity of a particle
2. Momentum change & time taken between wall collisions
3. Find pV
4. Velocity can be in any direction, so find c = sqrt(vx^2 + vy^2 + vz^2)
5. On average, only 1/3 particles will travel in one plane.

pV = 1/3 Nmc^2

Question 15

Internal Energy

Answer 15

deltaU = Q - W

U = ΣEk + ΣEp, but ΣEp = 0 for ideal gases

Question 16

Mass Defect

Answer 16

Difference between predicted and actual mass of particles

Question 17

Binding Energy

Answer 17

E = [mass_defect]c^2 gives the energy needed to dissociate a nucleus into its constituent nucleons.

Question 18

Amplitude

Answer 18

Maximum displacement from equillibrium in an SHM system.

Question 19

Free / Natural Oscillations

Answer 19

Occur when an SHM system is displaced, causing it to return to equillibrium via oscillation.

Question 20

Resonance

Answer 20

Occur when a system is supplied by energy from an SHM system via a driving force.

Question 21

Resonant / Natural Frequency

Answer 21

When a system reaches a specific frequency, its amplitude is maximised.

Question 22

Method For Analysing

Answer 22

1. Measure bg radiation with no absorbers
2. Measure source radiation
3. Measure with paper, add aluminium foil and measure again (and repeat with several meters of concrete in between source and detector)
4. If count drops with paper, alpha is present
   If count drops FURTHER with aluminium foil, beta is present.
   If count is above bg level, gamma is present (drops FURTHER with concrete, gamma is present).

Question 23

Continuous Decay Rate

Answer 23

N = N₀e^-λt
A = A₀e^-λt

Question 24

Discrete Decay Rate

Answer 24

N = N₀ / 2^x
A = A₀ / 2^x

Question 25

Alpha, Beta, Gamma

Answer 25

Alpha is a helium nucleus
Beta is an electron
Gamma is a photon

Question 26

Bacquerels

Answer 26

A = λN