2020 free WAEC PHYSICS ANSWERS
2020 free WAEC PHYSICS ANSWERS

 Physics 2 (Essay) – 09:30 a.m. – 11.00 a.m.

 Physics 1 (Objective) – 11:00 a.m. – 12:15 p.m



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section A Answer 5 Only

(8a) Uniform acceleration is the state of motion of a body that maintains equal velocity in equal time intervals ie a condition where the rate of change of velocity is constant. 

(bi) 
-Frictional force 
-Force due to the motion of the car. 

(8bii) 
^
-Gravitational force | 

-Reaction |


(8ci)
Draw your diagram [Click here to view the diagram
[Click here to view the continuation of the diagram]

(8cii) 
The total distance travelled by the car is the Area of the trapezium; given by A=1/2{a + b}ha
a =30m, b = 60, h = 25
A = 1/2{30+60}25
A = 1/2(90)25
= 45 × 25 = 1,125m²

(8cii) 
Decelartion of the car,
a = v/t = 25/10m/s = 2.5m/s2
a= -2.5m/s2

(8d) 
Work done on a stretched string 
=1/2Fe = 1/2×12×0.5 ×10-²
Since F = 12N
e= 0.5cm = 0.5×10-²m

Workdone = 1/2×12×0.5× 10-²
=0.03Nm-²



(11ai)
Reactance is the opposition offered to the passage of an alternating current by either the inductor OR the capacitor or both. 

(11aii)
Impedance is the overall opposition of a mixed circuit To the flow of an alternating current in a ressistor OR capacitor. 

(11bi)
E.m.f is induced in an a.c generator so as to create more magnetic flux which generates an induced current. 

(11bii) 
The carbon brushes makes contact with the springs so that the amature rotates through it. Induced current will be produced. It also used to alternate the direction of the current produced. 

(11biii) 
The law states that if the first three fingers of one's right hand are held at right angles to each other with the fore finger in the direction of the the field and the third in the direction of the motion, the middle finger points in the direction of the induced current. 

(11biv) 
-Increasing the no of coils. 
- The presence of soft iron core inside the coil. 

(11c) 
Energy E = power × time
E = pt; where p=6w, t=60mins
E= 6 ×5 ×60
= 180J


(9ai) 

(i) Nature of the Substance 

(ii) Medium of transmission 


(9aii)

(i)State or phase of the substance (i.e Solid, Liquid or gas). 

(ii)Temperature of the medium 


(9b) 

(i) Temperature 

(ii) Specific hear capacity of the body


(9c) 

The statement means that the amount of hear energy required to change 1kg of liquid mercury to gaseous mercury without change in temperature is 2.72×10^5Kg-¹


(9c) 
The statement means that the amount of hear energy required to change 1kg of liquid mercury to gaseous mercury without change in temperature is 2.72×10^5Kg-¹

(9di)
Please Note D means "Change Sign"
Q=MCDQ
V²/R × t=MCπQ
(220)²×4×60/35=M×4200×(100-28)
33,885.7=302400m
M=33,885.7/302400
M=1.098kg

(9dii) 
V²/R ×t=MLv
(220)²×5 ×60/35=0.3×Lv
414857.14=0.3Lv
Lv=414857.14/0.3
Lv=1382857.13Jkg-¹


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(10a)

Diffraction is the ability of waves to bend around obstacles in their path


(10bi)

Critical angle is the highest angle of incidence in a denser medium when angle of refraction in the less dense mediumis 90 degrees


(10bii)

Critical angle=90-44=46°

The refractive index of the glass is obtained as follows

The refractive index(n)=sini/sinr=sin46/sin90=0.7193/1

=0.7193


(10ci)

fo=200Hz

f1=3v/4l =>closed pipe

f1=v/l=>open pipe

but 3fo=f1=>closed pipe

3×200=f1=>f1=600Hz

Also f1=2fo=>open pipe

2fo=600

fo=600/2=300Hz


(10cii)

v=330m/s

L=?

fo=200Hz

fo=v/4l

=>200=330/4l

800l=330

l=330/800

l=0.4124m


(10ciii)

fo=v/2l

fo=300Hz

v=330m/s

300=330/2l

l=330/600

l=0.55m


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12) CLICK HERE FOR IMAGE

      CLICK HERE FOR CONTINUATION 


(12a) This is defined as the amount of energy that must be supplied to a nucleus to completely separate it's nuclear particles (nucleons)

(12b) 
(i) They have short wavelength and high frequency. 
(ii) They are highly penetrating. 
(iii) They travel in straight lines. 
(iv) They don't require material medium for their propagation.

(12c) 
-It is used in production of electricity. 
-It is used to study and detect charges in genetic engineering. 
-It is used in agriculture. 
-It is used in treatment of cancer. 

(12di)
E = hf-hfo
but f = v/landa
E= v/landa.h - wo
Where wo = hfo = work function 
f= frequency 
landa = wavelength 
Hence 
hf = hfo - E
f = hfo - E/h
f = wo - E/h
Recall; that v = f landa
Therefore f = v/landa = 3×10^8/4.5×10-7
=3/4.5 × 10^8+7
=6.6×10^14Hz
f = 6.6×10^14Hz

(12dii) 
E = hf
=6.6×10^-34 × 6.6×10^14Hz
=43.56×10^-20J

(12diii) 
Energy of the photoelectron E = hf - vo
=Energy of incident electron - work function 
=4.356×10^-19J - 3.0×10^-19J
=1.356×10^-19J


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(7a)
LASER stands for Light Amplification by Stimulated Emission of Radiation. 

(7b) 
Laser is a device that generates an intense beam of coherent monochromatic light or other electromagnetic radiation by stimulated emission of photons from excited atoms or molecules. 



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(1a)
Strain can be defined as the ratio of extension per unit length
Strain=extension/length

(1b)
Strain=extension/length
Let original length=L
Final length=2L
Extension=2L-L=L
Strain=L/L=1

Strain = change in length / original length



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(6)

Given constant = 2.9×10-³mk

Temperature = 57d°C = (57+273)k = 330k

Using landamaxT = constant 

landamaxT330 = 2.9×10-³

landamax = 2.9×10-³/330

landamax = 8.788×10^-6m

The speed of electromagnetic wave, v = 3×10^8m/s

Using V = f landa

f = v/landa

=3×10^8/8.788×10^-6

=3.4×10¹³Hz



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(5)
Range = u²Sin2tita/g
At maximum range 
Sin2tita = 1
2tita =sin-¹(1)
2tita = 90dgrees 
Tita = 90/2 = 45°

Maximum height reached = u²sin²tita/2g
=u²(sin45)²/2g
=200²(sin45)²/2(10)
=40000(1/√2)2/20
=40000(1/2)/20
=20000/20
=1000metres.


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2)

i) Silicon Dioxide

ii) Silica Powder

iii) Germanium Tetrachloride


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3)

i) Ferromagnetic material

ii) Diamgentic material

iii) Pamangentic material


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