WAEC GCE 2018 Physics (Obj & Essay) Answer – Nov/Dec Expo

 

*WAEC GCE 2018: CONFIRMED PHYSICS ESSAY SOLUTIONS

Physics-Obj
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(1a)
Young modulus of a material or the modulus of
elasticity.
(1b)
Potential Energy to kinetic Energy.
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(2)
e = 0.7m
m=60 × 10^-3kg = 6.0×10^-2kg
K = 200Nm^-1
W = 1/2ke² = 1/2mv²
1/2ke² = 1/2mv²
V² = ke²/m = 200×0.7²/6.0×10^-2
V² = 98×10²/6
V² = 16.33×10²
V = √1633
V = 40.4
Speed = 40.4ms^-1
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(3)
(i) Optical fibres have extremely high bandwidth
(ii) They have longer transmission distance
(iii) They have resistance to electromagnetic
interference
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(4a)
It is used in geometric stations used to move a
satellite from low earth orbit into a
geostationary orbit.
(4b)
Polar orbit satellite is used in earth mapping.
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(5a)
(i) Centripetal force
(ii) Centrifugal force
(5b)
Ft = mDv
where F = force
t = time
Dv = change in velocity
m = mass of object
Hence F = mDv/t
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(6a)
(i) It can cause short and long term sun burn
effects.
(ii)It can cause blindness when flashed to the
eyes.
(6b) Energy = hf
= 6.60×10^-34 × 4.82×10^14
= 3.18×10^-19J
= 1.99ev
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(7)
V = 2πR/T
R = 9.6×10^6 + 6.4×10^6 =16×10^6 m
T = 24hrs =(24×60×60)s
V = 2×3.142×16×10^6/24×60×60
V = 1162.96m/s
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8a) Mass is the amount of material contained in a body and the SI unit is Kg while Weight is the force exerted on a body by the gravity of the object. ..Mass is a scalar quantity( It has not specific direction), While Foce is a vector quantity (Its in the same direction with gravity)
8ai)
Mass is measured in Kg
Weight is measured in Newton
Mass is a scalar quantity
Weight is a vector quantity
Mass is constant
Weight varies
8aii) Clockwise moment about the pivot.
Moment = Force x Distance
Moment = 250 x 0.75
Moment = 187.5Nm
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(11a)
Lenz’s law states that an induced current is in
such direction that it’s magnetic effect opposes
the change by which the current is induced.
(11b)
(i) Magnets are used in construction of
speakers.
(ii) They are used to store data in computers.
(iii) Used in magnetic resonance imaging
machines.
(11ci)
(a) Two coils: So as to produce an induced
current from one coil to the other.
(b) an iron core: To increase the strength of the
magnetic field.
(11cii)
(11d)
Total resistance in series
Rt = R1 + R2
= 500 + 400
Rt = 900ohms
Taking E = 6v
E = V + ir
E = VR + Ir
E = I ( R + r)
I = E/R + r
taking r = 200ohms
I = 6/900+200
I = 6/1100
I = 0.005A
Hence the voltmeter reading
V = IR
= 0.005 × 200
= 1.09v
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