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Posted By on September 14.
Found In: Waec
Source: , , ,

## Welcome to Waec 2021 Physics Answer

Welcome to Waec 2021 Physics Answer as I Congratulations for your search here as NAIJACLASS is the Number one Trusted Exam Specialists, An expert in all Exams Sector; we assist candidates to pass various examinations with ease. =============================

_____________
===============
PHYSICS OBJ:
01-10: AAABACCDDB
11-20: ACCDCBCBAC
21-30: CCCBBDDBBB

===========================

PHYSICS THEORY
_____________
(1)
Workdone = 1/2Fe
= 1/2 × 40 × 1/100
= 1/5 = 0.2J
===========================

(2a)
(i)Navigation satellites e.g global position system – GPS
(ii) Communication satellites eg ANIK

(2b)
V = 2πR/T
For every second,
Speed, V = 2πR
V = 2 × 22/7 × 6300
V = 39,600km/s
===========================

(3)
V=u cosθ -gt
V=40*cos30-10*1
V=34.64-10
V=24.64m/s
===========================

(5a)
Wave particles duality is the concept in quantum mechanics that every particles or quantum entitle may be described as either a particle or wave.

(5b)
λ=h/MV
4.2*10^-¹¹=h/1.6*10^-²³
h=4.2*10^-¹¹ * 1.6*10^-²³
h=6.72*10^-³⁴
===========================

(6)
(i)reflection
(ii)refraction
(iii)diffraction
=============

(1, 2, 3 & 5) =============================

(8)  =============================

(9) =============================

(11)  8ai)
Hooke’s law states that the extension e produced by an elastic material is directly proportional to the applied force provided the elastic unit is not exceeded.

(8aii)
(i) Given extension, e = I2 – I1 = 0.75 – 0.20 = 0.55m
Force applied, Fe = (1.95 – 0.30) × 10
= 1.65 × 10 = 16.5N
Force constant , K = F/R = 16.5/0.55 = 30N/m

(ii) Using F = K (I1 – Io)
m1g = K ( I1 – Io)
= 0.30 × 10 = 30(0.20 – Io)
= 0.10 = 0.20 – Io
Io = 0.20 – 0.10
Io = 0.10m
Length of spring when it was unloaded = 0.10m

(8bi)
Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration.

(8bii)
(i) Temperature
(ii) Size of particles

(8biii)
Rate of diffusion is inversely proportional to the square root of density under given conditions of temperature and pressure. ie R ∝ 1/√d

(8c)
T = circumference of the orbit/orbit velocity
T = 2πR/v
But V = √GM/R
T = 2π√R³/GM

11ai)
Root measurement value of an alternating current is the value of A.C current that has the same heating affect as a D.C current

(11aii)
Impedance is the affective resistance of an electric circuit arising from the combined affects of ohmic resistance and reactance .( ie resistors, indicators and capacitors)

(11b)
Current in circuit , I = 60/120 = 0.5A
Voltage across device , Vr = 120V
Voltage across capacitor , Vc = √V² – Vr
Vc = √240² – 120²
Vc = 207.846V
Ic = I = 0.5
Xc = Vc/Ic = 207.846/0.5 = 415.7Ω
Capacitance, C = Xc/2πf = 415.7/2*3.142*50 = 1.323F

(11ci)
The capacitance of a capacitor is the ratio of the amount of charge on its plates to the potential difference between them. ie C = ∑/V

(11cii)
(i) Charge in both capacitors are the same
∑1 = Q2
ie C1V1 = C2V2 ………(1)
Total capacitance ,C = C1C2/C1+C2
C = C2/1+C2/C1 = C2/1+V/V2
C = C2V2/V1+V2 = C2V2/2
C= 1/2C2V2

(ii)Voltage across, V1 = (C2/C1+C2) × V
V1 = (C1/C1+C2) × V
But C1/C2 = d2/d1 = 5/2
V1 = (1/(5/2+1)) × 2 = 2/7 ×2 = 4/7Volts
Voltage across, C2 : V2 = 2-4/7 = 10/7volts
=============================

(12ai)
A radioactive nucleus is said to be relatively stable if it does not further disintegrate or form any other atomic nucleus

(12aii)
Reason; The more the atomic mass of a nucleus, the more it’s radioactive tendency an the lesser it’s stability

(12bi)
Ionization potential is the amount of energy eV, which helps to remove an electron completely from an atom. It is represented with V.

(12bii)
E = eV
IeV = 1.6×10-¹⁹

V = hv/λ where h is the planks constant

h = 6.626 ×10-³⁴ , c = 3×10⁸m , λ = 1.02 × 10-⁷m

E = (1.6×10-¹⁹) × (6.626 ×10-³⁴) × (3×10⁸)/1.02 × 10-⁷

E = 31.805 × 10-⁴⁵/1.02 × 10-⁷
E = 31.2 × 10-³⁸ volts

Naijaclass is an online Platform; A subsidiary school news portal for aspirants, students, graduates and interested individual of various schools which kicked off July 1st, 2014 with an aim of providing useful and valuable information about Higher Institutions News, Online CBT Practice for WaecNecoNabteb & Jambite, Scholarships, Study-abroad, health, Career and much more to students at all levels of education to happy visitors About us in Nigeria and in the diaspora.

### At Naijaclass.com, we have so many activities to engage our students in order to help them find what they are looking for in all levels of education

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 COMMENT SECTION

### One Response

• Good job
Thanks for that

Grace Sep 15, 2021 11:27 am

Posted By on September 14.
Found In: Waec
Source: , , ,

## Welcome to Waec 2021 Physics Answer

Welcome to Waec 2021 Physics Answer as I Congratulations for your search here as NAIJACLASS is the Number one Trusted Exam Specialists, An expert in all Exams Sector; we assist candidates to pass various examinations with ease. =============================

_____________
===============
PHYSICS OBJ:
01-10: AAABACCDDB
11-20: ACCDCBCBAC
21-30: CCCBBDDBBB

===========================

PHYSICS THEORY
_____________
(1)
Workdone = 1/2Fe
= 1/2 × 40 × 1/100
= 1/5 = 0.2J
===========================

(2a)
(i)Navigation satellites e.g global position system – GPS
(ii) Communication satellites eg ANIK

(2b)
V = 2πR/T
For every second,
Speed, V = 2πR
V = 2 × 22/7 × 6300
V = 39,600km/s
===========================

(3)
V=u cosθ -gt
V=40*cos30-10*1
V=34.64-10
V=24.64m/s
===========================

(5a)
Wave particles duality is the concept in quantum mechanics that every particles or quantum entitle may be described as either a particle or wave.

(5b)
λ=h/MV
4.2*10^-¹¹=h/1.6*10^-²³
h=4.2*10^-¹¹ * 1.6*10^-²³
h=6.72*10^-³⁴
===========================

(6)
(i)reflection
(ii)refraction
(iii)diffraction
=============

(1, 2, 3 & 5) =============================

(8)  =============================

(9) =============================

(11)  8ai)
Hooke’s law states that the extension e produced by an elastic material is directly proportional to the applied force provided the elastic unit is not exceeded.

(8aii)
(i) Given extension, e = I2 – I1 = 0.75 – 0.20 = 0.55m
Force applied, Fe = (1.95 – 0.30) × 10
= 1.65 × 10 = 16.5N
Force constant , K = F/R = 16.5/0.55 = 30N/m

(ii) Using F = K (I1 – Io)
m1g = K ( I1 – Io)
= 0.30 × 10 = 30(0.20 – Io)
= 0.10 = 0.20 – Io
Io = 0.20 – 0.10
Io = 0.10m
Length of spring when it was unloaded = 0.10m

(8bi)
Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration.

(8bii)
(i) Temperature
(ii) Size of particles

(8biii)
Rate of diffusion is inversely proportional to the square root of density under given conditions of temperature and pressure. ie R ∝ 1/√d

(8c)
T = circumference of the orbit/orbit velocity
T = 2πR/v
But V = √GM/R
T = 2π√R³/GM

11ai)
Root measurement value of an alternating current is the value of A.C current that has the same heating affect as a D.C current

(11aii)
Impedance is the affective resistance of an electric circuit arising from the combined affects of ohmic resistance and reactance .( ie resistors, indicators and capacitors)

(11b)
Current in circuit , I = 60/120 = 0.5A
Voltage across device , Vr = 120V
Voltage across capacitor , Vc = √V² – Vr
Vc = √240² – 120²
Vc = 207.846V
Ic = I = 0.5
Xc = Vc/Ic = 207.846/0.5 = 415.7Ω
Capacitance, C = Xc/2πf = 415.7/2*3.142*50 = 1.323F

(11ci)
The capacitance of a capacitor is the ratio of the amount of charge on its plates to the potential difference between them. ie C = ∑/V

(11cii)
(i) Charge in both capacitors are the same
∑1 = Q2
ie C1V1 = C2V2 ………(1)
Total capacitance ,C = C1C2/C1+C2
C = C2/1+C2/C1 = C2/1+V/V2
C = C2V2/V1+V2 = C2V2/2
C= 1/2C2V2

(ii)Voltage across, V1 = (C2/C1+C2) × V
V1 = (C1/C1+C2) × V
But C1/C2 = d2/d1 = 5/2
V1 = (1/(5/2+1)) × 2 = 2/7 ×2 = 4/7Volts
Voltage across, C2 : V2 = 2-4/7 = 10/7volts
=============================

(12ai)
A radioactive nucleus is said to be relatively stable if it does not further disintegrate or form any other atomic nucleus

(12aii)
Reason; The more the atomic mass of a nucleus, the more it’s radioactive tendency an the lesser it’s stability

(12bi)
Ionization potential is the amount of energy eV, which helps to remove an electron completely from an atom. It is represented with V.

(12bii)
E = eV
IeV = 1.6×10-¹⁹

V = hv/λ where h is the planks constant

h = 6.626 ×10-³⁴ , c = 3×10⁸m , λ = 1.02 × 10-⁷m

E = (1.6×10-¹⁹) × (6.626 ×10-³⁴) × (3×10⁸)/1.02 × 10-⁷

E = 31.805 × 10-⁴⁵/1.02 × 10-⁷
E = 31.2 × 10-³⁸ volts

Naijaclass is an online Platform; A subsidiary school news portal for aspirants, students, graduates and interested individual of various schools which kicked off July 1st, 2014 with an aim of providing useful and valuable information about Higher Institutions News, Online CBT Practice for WaecNecoNabteb & Jambite, Scholarships, Study-abroad, health, Career and much more to students at all levels of education to happy visitors About us in Nigeria and in the diaspora.

### At Naijaclass.com, we have so many activities to engage our students in order to help them find what they are looking for in all levels of education

 COMMENT SECTION
 COMMENT SECTION

### One Response

• Good job
Thanks for that

Grace Sep 15, 2021 11:27 am

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