NECO 2020 - PHYSICS ANSWER

PHYSICS OBJ
1-10: BCBDBDCDCD
11-20: DACBEBABDE
21-30: CDDDABBBAC
31-40: CDAEBBCCDC
41-50: BEEBDBAEEC
51-60: DDCDADDEBD
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(1ai)
[Choose ANY ONE]
-Printer
-Photocopy machine
-Label maker
-Document scanner

(1aii)
Sterilizer

(1b)
Draw the diagram.

(1c)
I = 1.26A
t = 4800s
m = ?
Z = 3.3×10^-⁴gc-¹
m = ZIt
m = 3.3×10^-⁴×1.26×4800
m = 1.996g


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(3a)
Velocity is defined as the rate of change of distance moved in a specific direction or the rate of change of displacement.

(3b)
U = 0m/a
V = 20ms-¹
t1 = 20s
t2 = 30s
t3 = 10s

Draw the diagram


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(5a)
[Choose ONLY ONE]
-They are both scalar quantity.
-They are both connected with work.

(5b)
R0 = 25ohms
R100 = 100ohms
R = ?
Tita = 67°c
Tita= Rtita-R0/R100-25 × 100
67 = R - 25/100 - 25 × 100
67 = (R0 - 25)/75 × 100
R0 - 25 = 67 × 75/100
Rtita - 25 = 50.25
Rtita = 50.25+25
Rtita = 75.25ohms


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((9a)
It simply means that the ratio of resistance and impedance is 1 and the maximum power is obtained in such circuit.

(9b)
V² = Vr² + Vc²
15² = 12² + Vc²
225 - 144 = Vc²
V = √81
Vc = 9


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(10a)
(i) Weight
(ii) Upthrust.
(iii) Viscous force.

(10b)
Both viscous force and upthrust acts in upward direction while weight act downward in order to balance the force

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(11i)

4 A 12 1
He + Be --> X + Y + Z
2 A B C

A = 9
B = 6
C = 1

(11ii)
Z = 0
e ie Beta particles.
-1

(11iii)
Nuclear fusion
W = v + u


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(12a)
(i) Friction.
(ii) Upthrust.

(12aii)
(i) Force causes motion
(ii) Force causes stress/strain

(12b)
Draw the diagram [https://i.imgur.com/j8jNZmi.jpg]

(12c)
Draw the diagram [https://i.imgur.com/j8jNZmi.jpg]
(i) Taking moment about pivot
CW moment = ACW moment
36×25 = X×15
X = 36×25/15 = 60g

(ii)
Draw the diagram[https://i.imgur.com/j8jNZmi.jpg]
60 × X = 36 × (30 - X)
60X = 1080 - 36x
96X = 1080
X = 1080/96 = 11.25
Distance = 11.25 from the zero end.


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(13ai)
(i) Dew
(ii) Mist

(13aii)
(i) Both require the supply of heat.
(ii) Vapour is expelled when both processes occur.

(13b)
An object initially at a height, say H has a tiny potential energy. As it falls and now at a height say h, the potential energy reduces and kinetic energy increases. The kinetic energy because it is equal to the P.E at height H when the object just strikes the ground.
NB: At any point, mechanical energy is conserved.

(13ci)
Given V.R = 5, Load L = 500N
Workdone against friction
= Total workdone - work output by system.
= 7200 - (500 × 12)
= 7200 - 6000
= 1200J

(13cii)
Efficiency = work output/work input × 100%
= 6000/7200 × 100%
= 83.33%


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(14a)
Given y = Asin2pie(t/T - x/lander)

(i)
T represents period.
Lander represents wavelength.

(ii)
T = 2pie/w
T = 1/f

(14bi)
(i) Microscope.
(ii) Telescope.

(14bii)
Refraction involves two media, while reflection involves one medium.

(14ci)
Frequenxy of wave f = v/lander
= 0.6/0.04 = 1.5 Hertz

(14cii)
Refractive index of water = speed in deep water/speed in shallow water.
= 0.8/0.6 = 4/3




(15a)
The potential difference between any two points in an electric field is defined as the work done in moving a positive charge of 1 coulomb from one point in the electric field to another.

(15b)
Diagram [CHECK THE DIAGRAM BELOW]

(15c)
Given: Power p = 1200w, Voltage v = 220v
(i)Resistance, R = v²/p = 220×220/1200 = 40.3ohms

(ii)
Energy consumed by one heater = Power × time
= 1200 × 5
= 6000watt-hours
= 6kWh
Energy consumed by 5 heaters = 5 × 6 kWh
= 30kwh
Cost = 30 × 4
= #1,020.00





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