2020 NECO PHYSICS OBJ AND ESSAY QUESTIONS AND ANSWERS

2020-Physics-Obj
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PHYSICS-Theory
PART II (Answer only Four (4) Questions
Only.
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(12ai)
(i)Push
(ii)Pull

(12aii)
– It causes the body to move
– It determines the direction of which the body moves

(12b) Parallelogram rules states that if the two sides of vectors are represented by the two opposite sides of a parallelogram the adjacent side drawn from a common point represent the resultant

(12ci)
From the principle of moment,
SAGW = SCW
36*25 = x*15
900 = 15x
x = 900/15
x = 60g

(12cii)
60x = 36(30-x)
60x = 1080 – 36x
60x + 36x = 1080
96x = 1080
x = 1080/96
x = 11.25cm

:. Distance from balance point = 25cm + 11.25cm = 36.25

(12)
Diagram

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(13ai)
(i)When the air is cooler to its dew point
(ii)When it becomes so saturated with water vapour that it cannot hold any more water

(13aii)
(pick 2)
(i)Both the processes, water vapour sis given off from the liquid
(ii)Both are dependent on the vapour pressure
(iii)At the end of both processes, they result in the change of state from liquid to vapour

(13b)
When a body is dropped from a certain height,the potential energy gradually changes into kinetic energy on reaching the ground,the whole of its potential energy gets converted into kinetic energy. But when the ball strikes the ground, the kinetic energy is converted into sunlight and heat

(13ci)
Total workdone = Workdone in raising the load + workdone against friction

7200 = (500×12) + workdone against friction
Workdone against friction = 7200-6000 = 1200J

(13cii)
Efficiency = Work output/Work input × 100%
= 500×12/7200 × 100%
= 6000/7200 × 100%
= 83.3%
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(14ai)
T = period
λ = wavelength
w = 2π/T

(14aii) T = 2π/w

(14aiii) T = 1/f

(14b)
Vshallow = fshallow × λshaddow
0.6 = fshallow × 0.04
fshallow = 15Hz
fshallow = fdeep
f = 15Hz

(14c)
Refractive index= Vdeep/Vshallow
= 0.8/0.6 = 1.33
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(15a)
Potential difference is the measure of the Carrier of charge in a circuit it is measured in volts

(15b)
(Diagram And Explanation Below)

A varying currents of audio frequencies for in the speech coil when it is working. The force varies at the same frequency as the currents. The vibration of the diaphragm create sound waves as a result of the magnet. A soft iron piece is positively wound around an insulated wire many tones. This act as the speech coil when a varying speech current flows into the earpiece, the strength of the electromagnetic formed varies of the same frequency as the speech coil.

(15ci)
P=v²/R
1200=220²/R
1200R=220²
R=40.3Ω

(15cii)
Cost= p*t*unit cost
=1200 ÷100*5*34
=204
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(16a)
Based on the structure of solids, crystalline structure are those which are arranged in a repeated pattern or lattice eg Nacl while that of Amorphous is that which the atoms of the matter is scattered and have no order of arrangements eg plastic

(16b)
(i) Solids and liquids
(ii) Since the perfume is said to be move concentrated at that point would begin to diffuse rapidly from the region of high concentration until it evenly distributed to all parts of the room

(16c)
The more the density, the greater the viscosity, cold liquid are said to be more densed than that of hotter liquids due to that they have more viscosity. A palm oil is a typical example

(16di)
T1/2 = 0.693/λ
T1/2 = 0.693/0.01155
T1/2 = 60 days

Half life = 60 days

(16dii)
dN/ft ∝ No
dN/dt = λNo
dN/dt = 0.01155 × 250
dN/dt = 250.01155

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PART I
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(1a)
(i)printing machine
(ii)sterilizer

(1b)
Diagram (step up transformer)

(1c)
1=1.26
t=48005
m=?
z=3.3*10^-⁴g
m=3.3*10^-⁴*1.26*4500
=1.996gram
≅2gram
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(2a)
A system is unstable when displaced, it experiences a net force in the same direction as the displacement from equilibrium. It tends to accelerate away from its equilibrium position if displaced even slightly while for neutral equilibrium, the system is independent of displacement from its original position

(2b)
(ii)Low centre of gravity
(ii)Large surface area in contact
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(3a)
Velocity is defined as the rate of change in the displacement of a body it is a vector quantity with the S.I unit of ms-¹

(3b)
DIAGRAM

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(4)
At equilibrium position Point B, the body possess maxim kinetic energy. As it moves out to end point A and C. It stops momentarily before changing its direction.

(Diagram)

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(5a)
They are both derived quantities

(Diagram)

(5b)
67-0/100-0 = x-25/100-25
67/100 = x-25/75
61*3 = 4(x-25)
201 = 4x-100
4x = 201+100
4x = 301
x = 301/4 = 75.25 ohms
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(6a)
(i)violin
(ii)guitar

(6b)
The depth of field of a lens camera is less than that of a pinhole camera
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(7a)
– An amplifier
– A speaker

(7b)
u = 16cm
m = 4=v/u
:. v =4u
v = 4×16 = 64cm
Recall, 1/f = 1/u + 1/v
1/f = 1/16 + 1/64
1/f = 4+1/64
1/f = 5/64
f = 64/5 = 12.8cm
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(8a)
The zinc atoms on the surface of the anode oxidizes I;e they give up both their valence electrons to become positively

(8b)
Diagram

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(9a)
The power factor of a circuit is unity when the apparent power equals or some as the real power

(9b)
V=Vr+Vc
15=12+Vc
Vc=15-12
Vc=3v
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(10a)
(i)Viscosity
(ii)weight
(iii)upthrust

(10bi)
(i)Viscosity; the force in between the layers of flurds this force would tend to reduce the velocity at which the stone moves down till it reach terminal velocity

(ii)weight; is the actual force acting of the stone in the liquid.

(iii)upthrust; is the upward force felt by reply objects in flurd, due to the area displace
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(11i)
A=9 (molecular mass)
B=6 (atomic mass)
C=0

(11ii)
Z=Energy

(11iii)
Nuclear fusion

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Posted by admin on 27th September 2020.

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