2017 Free Expo Answers
============================
2017 NECO Expo Runs, Questions and Answers.
This great
opportunity to get grades like A’s, B’s and
Minimum of Credit in this exam and be Free
forever from O Level Issues Every Year.
PHYSICS-OBJ
1CEABCBAABB
11DCCBCBCCAE
21BECDDBEDDE
31DBAEADBABA
41CBDCBBBDCB
51CEDDCBAEAA
================================
COMPLETING 1000% ASURED
================================
================================
Tell Your Friends About Www.Hellogist.com.ng
================================
PHYSICS THEORY ANSWERS
PART A ANSWERS ONLY 6
1ai)
i)propellant
ii)nozzle
1aii)
i)used for comunication
ii)used for access geographically dispersed
terrains and uneven topography that
characterise the nations landscappe
1b)
Given: Object distance for eyepiece, U=3.0cm
Final image distance, V=?
Focal length of eyepiece, F=5.0cm
using the mirror/lens formular
1/f=1/u+1/v
1/5=1/3+1/v
multiplying through with 15v(1.cm)
3v=5v+15
3v-5v=15
-2v=-15/2
V=7.5cm
the final image is virtual and 7.5cm from the
eyepiece on the same side of the eyepiece as
the object
================================
2)
Given Radius, r=25m
linear velocity, v=20m|s
centripetal acceleration,a=?
Using:
a=V^2/r2
a=20^2/25
a=16m|s^2
================================
(4a)
The specific latent heat of vaporization of a
substance is the quantity of heat required to
change a unit mass of the substance from liquid
to vapour without change of temperature
(4b)
Kinetic energy is that possessed by a body due
to its motion. While potential energy is that
possessed by a body due to its height or state
================================
6a)
a wave front is the locus of points
characterized by propagation of position of the
same phase: a propagation of a line in 1D, a
curve in 2D or a surface for a wave in 3D. In
other words a line or surface in the path of an
advancing wave on which all the particles are
vibrating in phase is called a wave front.
6b)
i)plane wave front
ii)spherical wave front
================================
7)
Pupil- Regulates the amount of light entering
the eye
Shutter-admits or shuts off light from the film
of the camera
Screen-used to focus light from a near object in
front of the pinhold camere
================================
9a)
i)over charging (for secondary cell)
ii)self discharge (for primary cell)
9b)
self discharge- a primary cell lose a
considerable percentage of their charge when
stored at room temperature, this is due to non-
current-producing “side” chemical reactions
that occur within the cell even when no load is
applied
================================
10)
i)fusion is more easily achieved with lightest
elements such as hydrogen
ii)the raw materials required for fussion are
more cheaply and readily available
iii)fusion process produce less dangerous by
product
================================
PART B ANSWER 4 QUESTIONS
====
12ai) Newton’s second law of motion states
that the rate of change of momentum is
proportional to the impressed fotvr and takes
place in the direction of the force
12aii)- The motion of the strings in a musical
instrument eg. Guitar
– The motion of the balance wheel of a watch
12bi) Resultant force is that single force which
acting alone will have the same effect in
magnitude and direction as two or more forces
acting together
12bii) Equilbrum force is that single force
which will balance all the other forces taken
together. It is equal in magnitude buy opposite
in direction to the resultant force
12ci)
Resultant,Force,F=sqr4^2+3^2
F=sqr16+9
Fsqr25=5N
12cii)
using F=m(v-u)/t
5=5.5(v-2)/(5*60)
5*60*5=5.5(v-2)
=5.5(v-2)=1500
V-2=272.7
V=272.7+2
V=274.7m|s
final velocity of body = 274.7m|s
==================================
13ai)- Solar energy is for providing a cheap and
clean source of hot water supply.
– Solar energy provides electricity supply
13aii)-Renewable energy are those that can be
replaced as they are used up. They can be
continually replenished as they are exploited
and utilized while Non-Renewable energy are
those that cannot be replenished as they are
used up
-Examples of renewable energy are Solar
energy, wind energy, Biomass and Bio feuls
while examples of Non renewable energy are
Coal and wood, Fossil fuel, Petroleum and
Natural gas, Nuclear ener
==================================
(14ai)
A transverse wave is one which travels
perpendicularly to the direction of vibrations
producing the wave
(14aii)
-Light waves do not need a material medium for
its propagation but sound waves does
-Light waves cannot be plane polarized but
sound waves can
(14b)
Given y=4sin(1000pie*t/landa + 0.5x)
Comparing with y=Asin(2pie ft +2pie/landax)
(i) 2pie/landa=0.5
landa=2pie/0.5
landa=2*3.142/0.5
landa=12.56cm
Hence wavelength, landa=12.56cm
(ii) Also 1000pie/2pie*landa=500/landa
=500/12.56
=39.8Hz
f=39.8Hz
(iii)Speed V=flanda
v=500/12.56 *12.56
Speed v=500cm/s
v=5m/s
=================================
15a)
Coulomb’s Law state that the magnitude of the
electrostatic force between two point charges
is directly proportional to the product of the
magnitudes of the charges and inversely
proportional to the square of the distance
between them.
15bi)
diagram
R1
R2
R3
I<-V
15bii)
let equivalent resistance be R
1/R=1/R1+1/R2+1/R3
1/R=R2,R3+R1,R3+R1,R2/R1,R2,R3
R=R1,R2,R3/R1,R2,+R2,R3+R1,R3
15C)
Given; R=20n,C=4HF,F=50H2,TI=3.14
z=sqr R^2+(1/2TiFc)
z=sqr200^2+(1/2*314*50*4*10^-6)
z=sqr200^2+796.178^2
z=sqr40000+633900
z=sqr673900
z=8 21n
==============
Completed
==============