Prepared by:
Ridwan Abrar
Junior Year Undergraduate Student
Level-3, Term-2
Department of EEE, BUET
© All rights reserved
A word about significant figures which haunts everyone:
You are expected to have one s.f. more than the final answer required in a show that question, Most
people mess this up ;-;
Apart from that, work in 4 sf and give your final answer in 3 significant figures. Edexcel isn't very strict
about significant figures in theory papers.(Unit 4 and Unit 5)
Difficult Questions from Past papers:
1. October 2020: MCQ 4 and 7, 14b, 15c,16a, b(iii), 17 (b)ii) & iii) , c, 18b)i)
2. Jan 2020: MCQ 7,8,9; and 12, 15b, 17a), b), c) 18a), b)iii), 19 a)ii), b)
List of formulae:
Momentum:
p =mv
Δ(mv) Δp
F = Δt = t
p2
KE = 12 mv 2 = 2m
m1v1 = m2v2
Circular motion:
ω = Tθ ; w = angular speed, θ = angle in radians
1 ω
v = ω r, distance = θr ; f = T = 2π
2π
T = ω
v2
a= r = ω2 r
mv 2
F = ma = r = mω 2 r
Electric fields
kQ1 Q2 1
F = r2
; k= 4πε
1
,E= F
Q; E = electric f ield strength, N C −1 ; F = f orce on charge Q
kQ
E= r2
V
For the case of uniform fields, E is same everywhere, E = d
Capacitor
Q = CV; C is capacitance in Farads
μF = microFarad (10-6)
nF = nanoFarad (10-9)
pF= picoFarad (10-12)
2
W = 12 QV = 12 CV 2 = Q
2C
t t t
Q = Qo e− RC , V = V o e− RC ; I = I o e− RC
V = IR;
τ = RC = time constant
Time constant:
Time taken for the discharging current to become 37% of its initial value.
Time taken for the charging current to become 63% of final value
Usually, time taken to fully charge. discharge is about 5RC.
Magnetic fields
ϕ = BA ; ϕ = total f lux; B = magnetic f lux density; A = area
Φ = N ϕ = BAN ; U nit : W eber (W b)
F = B Il sinθ; maximum f orce occurs when θ = 90
F = B qv sinθ;
f lux change d(Φ) d(N ϕ)
induced emf = time taken
= dt
= dt
Particle Physics:
K E = eV = 12 mv 2
λ = hp ; λ = wavelength; h = P lanck ′s constant; p = momentum
E = VQ
E = mc2
p = Bqr ; p=momentum; B= magnetic field strength; r = radius; q= charge
2
,Momentum:
To be honest, there’s hardly anything significant that you can learn about this topic from books or notes.
Past papers are your only hope.
But a brief review on the basics:
Momentum = mass* velocity
m=p*v
Unit : kg m/s
Total momentum is always conserved in a collision.
Total kinetic energy may/may not be conserved.
Total kinetic energy is conserved only in case of elastic collisions.
If initial KE = final KE, elastic collision
If not, then inelastic collision
Newton’s 2nd law of motion in terms of momentum:
The force acting on a body is proportional/ equal to the rate of change of momentum (1)
and acts in the direction of change of momentum(1)
Alpha particles travelling faster
Alpha particle travel faster than any other new elements formed after radioactive alpha
decay because its mass is smaller or lighter
So higher speed for the same magnitude of momentum
The two new particles formed travel in opposite direction/ along a line
Experiment to find speed of 2 trolleys:
2 light gates (1)
Gate gives time trolley takes to pass (1)
Speed = length of interrupter/ time taken (1)
OR,
2 ticker timers;
dots at known time intervals;
speed = length of tape section/ time taken (1)
[ruler + clock could obtain 3rd mark only, specifying a length/time]
Law of conservation of linear momentum
Provided no external forces act on a body (1)
3
, Total momentum before collision = Total momentum after collision (1)
Why fragments shoot out in all directions when a nucleus breaks up
momentum (1)
zero/ negligible momentum before (1)
to conserve momentum fragments go out in all directions (1)
How tiny bacteria move is of interest in nanotechnology. Mycobacteria move by ejecting slime
from nozzles in their bodies. Explain the physics principle behind this form of propulsion.
Momentum conservation (1)
Total/initial momentum = 0 (1)
Momentum of slime equal to momentum of bacteria (1)
Bacteria moves in opposite direction (1)
OR
Force on slime (1)
Equal and opposite force on bacteria (1)
Cause rate of change of momentum / Δmv/t or ma to bacteria
Bacteria moves in opposite direction (1)
There is some uncertainty in the time a molecule with a particular mass will take to cover this
distance. Suggest two reasons for this. (June 2010, Q15d)
Some of the molecules in the sample will travel further / less/ not midway
Duration of laser pulse
Might emerge not horizontal
Molecules may be doubly/ integer ionised
Time very small
Not perfect vacuum/ collides with other molecules
Now check out this weirdo:
4
Ridwan Abrar
Junior Year Undergraduate Student
Level-3, Term-2
Department of EEE, BUET
© All rights reserved
A word about significant figures which haunts everyone:
You are expected to have one s.f. more than the final answer required in a show that question, Most
people mess this up ;-;
Apart from that, work in 4 sf and give your final answer in 3 significant figures. Edexcel isn't very strict
about significant figures in theory papers.(Unit 4 and Unit 5)
Difficult Questions from Past papers:
1. October 2020: MCQ 4 and 7, 14b, 15c,16a, b(iii), 17 (b)ii) & iii) , c, 18b)i)
2. Jan 2020: MCQ 7,8,9; and 12, 15b, 17a), b), c) 18a), b)iii), 19 a)ii), b)
List of formulae:
Momentum:
p =mv
Δ(mv) Δp
F = Δt = t
p2
KE = 12 mv 2 = 2m
m1v1 = m2v2
Circular motion:
ω = Tθ ; w = angular speed, θ = angle in radians
1 ω
v = ω r, distance = θr ; f = T = 2π
2π
T = ω
v2
a= r = ω2 r
mv 2
F = ma = r = mω 2 r
Electric fields
kQ1 Q2 1
F = r2
; k= 4πε
1
,E= F
Q; E = electric f ield strength, N C −1 ; F = f orce on charge Q
kQ
E= r2
V
For the case of uniform fields, E is same everywhere, E = d
Capacitor
Q = CV; C is capacitance in Farads
μF = microFarad (10-6)
nF = nanoFarad (10-9)
pF= picoFarad (10-12)
2
W = 12 QV = 12 CV 2 = Q
2C
t t t
Q = Qo e− RC , V = V o e− RC ; I = I o e− RC
V = IR;
τ = RC = time constant
Time constant:
Time taken for the discharging current to become 37% of its initial value.
Time taken for the charging current to become 63% of final value
Usually, time taken to fully charge. discharge is about 5RC.
Magnetic fields
ϕ = BA ; ϕ = total f lux; B = magnetic f lux density; A = area
Φ = N ϕ = BAN ; U nit : W eber (W b)
F = B Il sinθ; maximum f orce occurs when θ = 90
F = B qv sinθ;
f lux change d(Φ) d(N ϕ)
induced emf = time taken
= dt
= dt
Particle Physics:
K E = eV = 12 mv 2
λ = hp ; λ = wavelength; h = P lanck ′s constant; p = momentum
E = VQ
E = mc2
p = Bqr ; p=momentum; B= magnetic field strength; r = radius; q= charge
2
,Momentum:
To be honest, there’s hardly anything significant that you can learn about this topic from books or notes.
Past papers are your only hope.
But a brief review on the basics:
Momentum = mass* velocity
m=p*v
Unit : kg m/s
Total momentum is always conserved in a collision.
Total kinetic energy may/may not be conserved.
Total kinetic energy is conserved only in case of elastic collisions.
If initial KE = final KE, elastic collision
If not, then inelastic collision
Newton’s 2nd law of motion in terms of momentum:
The force acting on a body is proportional/ equal to the rate of change of momentum (1)
and acts in the direction of change of momentum(1)
Alpha particles travelling faster
Alpha particle travel faster than any other new elements formed after radioactive alpha
decay because its mass is smaller or lighter
So higher speed for the same magnitude of momentum
The two new particles formed travel in opposite direction/ along a line
Experiment to find speed of 2 trolleys:
2 light gates (1)
Gate gives time trolley takes to pass (1)
Speed = length of interrupter/ time taken (1)
OR,
2 ticker timers;
dots at known time intervals;
speed = length of tape section/ time taken (1)
[ruler + clock could obtain 3rd mark only, specifying a length/time]
Law of conservation of linear momentum
Provided no external forces act on a body (1)
3
, Total momentum before collision = Total momentum after collision (1)
Why fragments shoot out in all directions when a nucleus breaks up
momentum (1)
zero/ negligible momentum before (1)
to conserve momentum fragments go out in all directions (1)
How tiny bacteria move is of interest in nanotechnology. Mycobacteria move by ejecting slime
from nozzles in their bodies. Explain the physics principle behind this form of propulsion.
Momentum conservation (1)
Total/initial momentum = 0 (1)
Momentum of slime equal to momentum of bacteria (1)
Bacteria moves in opposite direction (1)
OR
Force on slime (1)
Equal and opposite force on bacteria (1)
Cause rate of change of momentum / Δmv/t or ma to bacteria
Bacteria moves in opposite direction (1)
There is some uncertainty in the time a molecule with a particular mass will take to cover this
distance. Suggest two reasons for this. (June 2010, Q15d)
Some of the molecules in the sample will travel further / less/ not midway
Duration of laser pulse
Might emerge not horizontal
Molecules may be doubly/ integer ionised
Time very small
Not perfect vacuum/ collides with other molecules
Now check out this weirdo:
4
