Waec 2019 Physics Theory & Objectives Exam Answers/Expo/Runz




PHYSICS OBJ:

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PHYSICS THEORY & OBJECTIVE ANSWER
(1)
Mass = 20g = (20/100)kg = 0.02kg
Extension = 5cm = (5/100)m = 0.05m
K = 200N/
V = ?
1/2mv² = 1/2ke²
V = √ke²/m = √200×0.05×0.05/0.02
V = √25
V = 5m/s
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(2a)
P - Initial velocity of the projectile
B - Angle of projection
H - Maximum height reached by the projectile
R - Range or the total horizontal distance covered by the projectile
(2b)
R=P^2 sin 2β/g
at maximum range sin2β=1
Rmax=P^2/g
This happens at β = 45degree

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Edited
(3)
(i)reflection
(ii)refraction
(iii)diffraction
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(4)
(i)Magnetic Declination
(ii)Horizontal Component of Earth’s Magnetic Field
(iii)The angle of Dip or Magnetic Inclination
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(5a)
Free electrons are electrons in a material which can contribute to electric current.
(5b)
hole is the absence of an electron in a particular place in an atom
(5c)
(5)
Draw the diagram

Using cosine law
Cos∅ = 16²+10²-14²/2(16)(10)

Cos∅ = 256 + 100 - 196/320

Cos∅ = 160/320
Cos∅ = 0.5
∅ = cos-¹(0.5)
∅ = 60°

Angle between 10N and 16N
= 180 - ∅ (sum of angles on a straight line)
= 180 - 60
=120°
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(6a)
Principle of operation of fiber optics state that the density of transparent glass and the refractive index is greater than the density of the two mirrors
(6b)
(i)it is used to view deep down the throat of a patient
(ii)it is used to conveying information
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(9a)
Latent heat is energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process.

(9aii)
(i)surface area in contact with atmosphere
(ii)nature of the liquid
(9bi)
Clay is poorer conductor of heat than plastic
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(9bii)
An increase in pressure in the cooker increase the ambient temperature in the cooker hence the food cooks faster
(9c)
(i)Change in the state of a substance
(ii)Increase in temperature
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(9di)
Heat supplied = m1
lvt = m1
12*40*1400=1.5*1
L=12*40*1400/1.5
L=672000/1.5= 448,000J/kg
Laten heat of fusion of the body = 4.48*10^5J/Kg
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(9dii)
lvt=mc D tita
12*40*72=1.5*c*60
C=12*40*72/1.5*60
C=384J/Kg/K
Specific heat capacity of the body =384J/Kg/K
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11) u= 5ms-1                                   u= 6ms-1
      A= 1ms-2                                     a= 3ms-2
     p→                                                        ←a

M—————————————N
                                51m


11a)t when particles are 30 meters apart
S= ut + ½ at2
Sp= st + ½ t2
Sa = 6t + 1/2 (3)t2
Where sp and sa are distances covered by particles respectively at any time t
At time, t= 1.5s
Sp = 5(1.5) +  ½(1.5)2 =8.625m
sa = 6(1.5) + ½ (3)(1.5)2 = 12.375m
sp + sa = 8.625 + 12.375
= 21m
Distance between particles = 51 – 21 = 30m
At time t = 1.5s, the particles will be 30 meters apart.
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