## Waec 2019 Physics Obj And Essay Answers – May/June Expo Runs

Physics OBJ:
1CBBBCACBBB
11BCCCABBCBB
21DCDADDBDDA
31BDDBBCAABC
41ABDABDCBBA

NOTE:
* means multiplication
/ means division
^ means raise to power
√ means square root

(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

(3)
(i)reflection
(ii)refraction
(iii)diffraction

(4)
(i)Magnetic Declination
(ii)Horizontal Component of Earth’s Magnetic Field
(iii)The angle of Dip or Magnetic Inclination

(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

(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

(8ai)
It state that every particles in the universe attract every other particle with a force that is proportional to the product of their masses and inversely proportional to the square of the distance between them
(8aii)
Gravitational field is a region of space around a mass on which the gravitational force of the mass can be felt

(8bi)
F=GMeM/re^2 ——from newton’s law
Where Me is mass of earth
re is the distance of mass from earth
G is a constant of gravitation
But F=GMeM/re^2 =mg
Me=GMe/re^2=g
g=GMe/re^2
(8bii)
(i)That The earth is a sphere
(ii)That g depends on mass of earth alone

(8c)
Using F = GMeM/r^2
F=6.67*10^-11*5.98*10^24*2.00*10^3degree/(1.50*10^8*10^3)^2
F= 79.7732*10^43/2.25*10^22
F=35.455*10^21
=3.5455*10^22N

(8di)
Escape velocity (Ve) is the minimum velocity required for an object (egg statelite) to just escape or leave the gravitational influence or field of an astronomical body (eg earth) permanently
(8dii)
(i)g varies across the earth but G is constant
(ii)the unit of g is m/s^2 while that of G is NM^2/Kg^2

(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
(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

(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
(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

(10)
FULL IMAGE – CLICK HERE

(11ai)
Force is anything that causes motion.Its S.I unit is Newton(N) or Kgm/s^2
(11aii)
(i) Static friction
(ii) Dynamic friction

(11bi)
DRAW THE GRAPH
(11bii)
Deceleration
during last 5s=18/5=3.6m/s^2
(11biii)
Total distance=S1+S2+S3+S4
=(30*20)+1/2(18+30)(6)+(18*10)=(1/2*5*18)
=600+144+180+45
=969metres

Posted on May 7, 2019