Waec 2016 Physics Obj And Theory Answers – May/June Expo

Physico-obj
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8a)
Net force: The net force is the vector sum of all the forces that act upon an object. It is also the sum of all the forces, taking into account the fact that a force is a vector and two forces of equal magnitude and opposite direction will cancel each other out.
8b)
The law of conservation of linear momentum states that the total
momentum of a system of particles remains constant, so long as no
external forces act on the system.
e.g Firing a bullet from a gun or a radioactive nucleus spontaneously emitting an alpha particle.
8c)
M = 200g = 0.2kg, h= 2cm, h2= 1.8m, u = 0, v=?
P.E = mgh
P.E = K.E = 1/2MV^2
4 = 1/2 x 0.2 x V^2
V = √40 = 6.32m/s^-1
Impulse = M(V-U)
Impulse = 0.2 ( 6.32 – (-o))
= 1.264Kgms^-1
8d)
M= 0.02kg , f= 5Hz, x= 10cm = 0.1 , V = 200cm = 2m/s
8dii)
r = ? , w = 2πf = 2×3.142×5
W= 31.4
From V= w √r^2 – 0.1^2
2 = 31.4 √ r^2 – 0.1^2
= r^2 – 0.1^2 = 0.6369^2
r^2 = 0.41564161
r = √ 0.41564161
r = 0.64m
Maximum vel
V = wr (x = 0 at maximum)
8diii)
maximum potential energy
=1/2 MVm^2
=1/2*20^10 *(372.3)^2
=10*138596.4
=1385964J
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10a)
Critical angle is the angle of incidence in the optically densed medium when the angle of refraction is 90degrees
10b)
Anti-note are created by region of maximum displacement in a wave
more coming
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11a)
Dielectric strength is the property of an insulating material to retain material to retain electrical properties
11bi)
-Infra-red wave
-Geiger muller counter
-Scintillation counter
11bii)
Irradiation of solar energy
11c)
Charge(q)=1.0*10^-19C
Electric field intensity(E)=1200NC^-1
Weight of the oil drop=?
E=F/q
1200=F/1.0*10^-19
F=1200*1.0*10^-19
F=1.2*10^3*10^-19
F=1.2*10^-16N
11d)
R=100ohm, L=0.05H, C=0.25uF
V=220v, f=50Hz
11di)
Impedance(z)=sqroot(R^2+(Xl-Xc)^2)
Xl=2*pie*fl
Xl=2*(22/7)*50*0.05
Xl=15.71ohm
Xl=(1/2*pie*fc)
Xc=1/78.55*10^-6
Xc=10^6/78.55
=12730.7ohm
Z=sqroot(100^2+(15.71^2-12730.7^2)
Z=sqroot(10000+2.63*10^16
Z=sqroot(2.63*10^16)
Z=1.62*10^16ohm
11dii)
Vrms=IZ
I=220/1.62*10^16
=1.36*10^-14
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9a)
i) thermal equilibrium is the point at which the temperature of an object remain constant or steady
ii)fundamental interval is the distance between upper and lower fixed point of a thermometre
9b)
i) it can be used to raise heavy load
ii) it is used in printing press
9c)
magnet
9di)
by using calometry law
heat last = heat gain
MmCmDθm=CaDθ + Mw Cw Dθ
300 * Cm * ( 85 – 40 ) = 90 + 500 * 4200
13500Cm = 90 + 29400000
13500CM = 29400090/13500
Cm=2177.78Jg^-K^-1
9dii) §
i) by convection
ii) by conduction
9diii) §
i) power generation
ii) chemical processing
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5)
i) For launching astronauts into the space
ii) For launching satellite
iii) For Scientific research
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6a)
Doping is the addition of small quantity of an element to a semi conductor to change its characteristics
6b)
Doping introduce impurities into an extremely pure instrintic semi conductor for the purpose of modulating its elctrical properties
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7)
X = Electron gun
Y = Accelerating mode
Z = Deflection plate
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3)
-smoke
-aerosol
-dust particle
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1a)
impulse(I)=F*t
F=ma= m(v/t)= M((d/t)/(t))
f=M(l/T)/T)= MLT^-2
I=MLT^-2 * T
I=MLT^-1
1b)
Acceleration(a)=v/t=(d/t)/t
a=d/t^2= L/T^2= LT^-2
1c)
WOrk(w)=f*d
W=MLT^-2 * L
W=ML^2T^-2
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4)
Given flux density(B)=0.217
Force(F)=9.6*10^-12N
Speed(v)=?
F=Bqv
9.6*10^-12= 0.12* 1.6* V
V=(9.6*10^-12)/0.192*10^-19
=50*10^-12+9
v=50*10^7
=5*10^8ms^-1
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2)
Velocity(u)=20ms^-1
Angle(tita)=40 degree
At maximum height, h
V^2=u^2 + 2gh
U^2 sin^2 tita+u
u= 20^2* (sin 40 degree)^2
u=20^2*(sin 4o degree)
u=400* 0.3455
u=138.2ms^-1

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