# 2018 WAEC GCE Physics Questions and Answers

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# 👑 2018 WAEC GCE PHYSICS ANSWERS👑

1. kilogram, meter and second
2. Vernier caliper
3.
4. gravitational force
5. Average velocity
6. ohm
7. slope of the lonear portion (AB)..
8. the adhesion btwn water and glass molecules is greater than the cohesion among the water molecules
9. 2.0 ms-2
10. u2/2g
11. Temperature
12. Temperature of the liquid
13. 0.5Ns
14. Screw jack
15. 4.69mm
16. Nm^2 Kg ^-2
17. Electric to heat
18. Temperature
19. 1000.oJ
20. Q will be less than pressure at R
21. 98.6 degreeF
22. Polarized
23. red
24.
25. 0.04m
26. elasticity
27. I and III only
28. 1/24cm
29.
30. real, magnified, inverted
31. 0.250ms^-1
32. sinusoidal
33. Low value resitor connected accross an AMMETER
34.
35. Increase in the distance btwn the plates
36. GHC 79.20
37. 0.5 height and 4.0m width
38. 400ms^-1
39. mechanical, heat and sound energy
40. doubling the inductance
41.
42. Longer and thinner
43.
44.
45. 6 ohms
46. Henri Becquerel
47. both energy and momentum
49. Have long wavelength
50. 1.02×10^-7

(1a)
Young modulus of a material or the modulus of elasticity.

(1b)
Potential Energy to kinetic Energy.
=========================================

(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
====================================

(3)
(i) Optical fibres have extremely high bandwidth
(ii) They have longer transmission distance
(iii) They have resistance to electromagnetic interference
=========================================

(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.
===========================================

(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
========================================

(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
=====================================

(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
=====================================

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

8bii (the value of F)
Clockwise moment = Anti clockwise moment
Fx(1.5+0.75) + 50x 0.75 = 250 x 0.75
F x 2.25 + 37.5 = 187.5
2.25F = 187.5-37.5
2.25F= 150
F = 150/2.25
F= 170.83N
========================================

(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

V = IR
= 0.005 × 200
= 1.09v
===================================

(12a)
(i) Cosmic rays
(ii) Rocks and soils

(12b)
Because the mass of a radioactive isotope decreases exponentially. Also, the source and intensity of radiation differs.

(12c)
(i) Dielectric materials
(ii)

(12d)