# 2020 WAEC Physics Theory/OBJ/Essay Questions and Answers

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Friday, 28th August 2020

Physics 2 (Essay) 9:30 am – 11 am
Physics 1 (Objective) 11:00am – 12:15pm

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PHYSICS OBJ:
1-10: DCCAACDCCC
11-20: BDACABDCCB
31-40: BDDBAACCCA
41-50: CAAABBCBBC

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(1)
Original length Lo = 3m
Extension e = 310 = 3*3 = 9m
F×e
F = ke where k = 982.3NM-²
F = 982.3*9 = 8,840.7N
The five that produce the extension F = 8.840.7N

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(2a)
Metal flat plate: It is a collector of heat that converts the radiant solar energy from the sun into heat energy by the process of greenhouse effect.

(2b)
Thermal Insulator: It prevents loss of accumulated heat in the solar collector and thereby improves its absorption efficiency.

(2c)
Tubes: They are use to capture almost all the sun’s energy. It is the most effecient solar collector
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(4)

V∝ Tx μy
LT-∝(MLT-²)x(MLT-¹)y
LT-¹∝ m*L*T-²x x m y L-y
LT-¹∝ m(x+y)L(x-y)T-²x
Comparing
X-y=1
X+y=0
-2x=1
From equation 3
X=½
Putting x = ½ into (eq) 2
y=-½
Equation is
V∝ T½ μ-½
V∝ √T/μ
V= k√T/μ
Where k is constant

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(5)

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(6)
Angle at horizontal θ = 30°
Time of light , T = 25sec
Velocity of projection u = ?
But T=2using sinθ/g
25= 2u*sin30/10
25=0.5u/5
0.5u=125
U=125/0.5
=250ms-¹

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(8a)
A torque or moment of a couple is the product of one of the forces and the perpendicular distance between the lines of action of the two forces.

(8aii)
(i)The two forces must be equal
(ii)The two forces must be opposite parallel
(iii)They must be equal distance between them

(8bi)
Free fall is defined as the motion of the body where gravity is the only force acting upon it.

(8bii)
Height of tower H = 40.0m
Velocity v = 10.0m/s, time t= ? , g=10.0m/s

Using the relation
S= ut + 1/2gt^2
H= ut + 1/2gt^2
40= 10t + 1/2*10t^2
4= t + t^2/2
= t^2 + 2t – 8=0 ( solving quadratically)
= (t+4)(t-2)=0
t+4=0 or t-2=0
t= -4 or t=2

Therefore time to fall on the ground t=2s

(8c)
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(9)