WAEC 2022 PHYSICS ESSAY AND OBJ ANSWERS

(9aii)
Given r = 5.28×10-¹¹m
k = 9.0×10⁹mF-¹
q₂ = q₁ = 1.6×10⁻¹⁹C = q
Electrostatic force F = kq²/r²
F = [9.0×10⁹(1.6×10⁻¹⁹)²]/(5.2×10⁻¹¹)²
F = 0.852×10⁻¹⁶N
F = 8.52×10⁻¹⁷N

(9bi)
(i) Current I = Vin/R₁+R₂
I = Ir₁ =Ir₂
Vout = Vr₂ = Ir₁ x R₂
Vout = [Vin/(R₁+R₂)] x R₂
Vout = Vin[R₂/(R₁+R₂)]

(ii) Given;
Vin/Vout = (R₁+R₂)/R₂ = 2.5
Where R₂ = 30Ω
(R₁+30)/30 = 2.5
R₁+30 = 75
R₁ = 75 – 30
R₁ = 45Ω

(9bii)
The volt is the work done of one joule in taking one coulomb of positive charge from one point to another.

(9c)
A wooden core cannot provide path to the flux which is needed to link either the secondary or primary side

(9d)
Used in medicine for visual functions
(9)


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(8ai)
The law of inertia states that a body will continue in its present state of rest or if it is in motion, will continue to move with uniform speed in a straight line unless it is acted upon by a force.

(8aii)
When the brakes of the moving vehicle are suddenly applied, or the passengers jerks forward as thet tend to continue in a straight line. The seat belt helps to provide a backward force and reduces injuries.

(8bi)
The moment of a force about a fixed point is the product of the force and the perpendicular distance at the point to the line of action of the force.

(8bii)
(I) Draw the Diagram

(II) clock wise moment = Anticlock wise moment
T x 1.5 = 54 x 0.5
T = 54×0.5/1.5
T = 18N

(III) F + T = w
F = w – T
F = 54 – 8
F = 36N

(8c)
[TABULATE]

=STATIC FRICTION=
(i) Independent of surface area in contact
(ii) Depends on normal reaction ( of one solid surface on the other)
(iii) Occurs between solids surfaces in contact

=VISCOSITY=
(i) Depends in surface area in contact
(ii) Independent of normal reaction
(iii) occurs between fluid layers/solid and fluid in contact/in fluids
(8d)
By increasing the number of pulleys.

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(7)
(i) Magnetic materials are materials having a magnetic domain and are attracted to an external magnetic field WHILE Non-magnetic materials are materials that are not attracted to an external magnetic field.
(ii) The magnetic domains of magnetic materials are aligned either parallel or antiparallel arrangements thus they can respond to a magnetic field when they are under the influence of an external magnetic field WHILE The magnetic domains of non-magnetic materials are arranged in a random manner in such a way that the magnetic moments of these domains are cancelled out. Thus, they do not respond to a magnetic field.
(iii) Magnetic materials are used to make permanent magnets are the parts of operating systems where magnetic properties are required WHILE Non-magnetic materials are used to make parts of some operating systems where no magnetic effect are expected and other things such as cases of compasses.
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(1)
Range|PQ| = U²Sin2Θ/g
Where U = 250ms-¹, Θ= 42°

= 250²×Sin(2×42°)/10
= 62,500×Sin84°/10
= 6250×0.9945
= 6215.63m
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(4)
Given;
F=50N, K=100N/m
But,
F= k.e
Therefore, 50=100 x extension(e)
e= 50/100
= 0.5m
But,
Workdone = 1/2(F x e)
=1/2(50 x 0.5)
=1/2(25)
=12.5Nm
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(12a&b)

(12c)


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(2)
(i) Their electrical conductivity is low
(ii) They are pure semi conductors with impurities less than 1 and have tetravalent crystals
(iii) Charges are obtained as a result of thermal excitation
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(5a)
A geostationary satellite is an earth-orbiting satellite, placed at an altitude of approximately 35,800 kilometers (22,300 miles) directly over the equator, that revolves in the same direction the earth rotates (west to east).

(5b)
(i) Gas Lasers
(ii) Solid-State Lasers
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