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# NECO Physics Obj And Theory 2017 Expo Answer

NECO Physics OBJ, ESSAY/Theory Questions and Answer – May/June 2017 Expo Runz

PHYSICS OBJ:

1CEABCBAABB
11DCCBCBCCAE
21BECDDBEDDE
41CBDCBBBDCB
51CEDDCBAEAA
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1ai)
i)propellant
ii)nozzle
1aii)
i)used for communication
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)
linear velocity, v=20m|s
centripetal acceleration,a=?
Using:
a=V^2/r2
a=20^2/25
a=16m|s^2
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
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)
i)a swinging pendulum
ii)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)
i)Solar energy is for providing a cheap and clean source of hot water supply.
ii)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
13b)
The principle of conservation of linear momentum us also utilized in the propulsion of jet aircraft. Gases are burnt within the combustion chambers of the engine. As jets of hot gases are expelled downwards through the tail nozzle at very high speeds from the aircraft, an equal and opposite momentum is given to the rocket or aircraft which then moves
13c)
Given: mass, m=0.2kg
heat lost,it=4200J
intial temperature cost r= 100’C
final temperature cost=?
S. It . c of water, C10=4200J/kg/k
using:
heat lost= M10, C10 (cost-tf)
400=0.2*4200*(100-costf)
=4200/0.2*4200
100-costF=5
100-5=costf
=cost=100-5
costf=95’C
final temperature=95’C
14ai)
A transverse wave is one which travels perpendicularly to the direction of the vibration producing the wave.
14aii)
i)Light Wave do not need a material medium for preparation, but sound wave does
ii)Light wave cannot be plane polarised but sound wave can
14b)
Given Y= 4sin (100×22/7xt/2 + 0.5x)
Comparing with
Y = A sin (2xPIxft + 2pi/pi x) Note : {the PI is the 22/7}
14bi)
2 x 3.142/0.5 = 12.56cm
Hence Wave length is 12.56
14bii)
Also 1000PI/wave length = 2PI F
= 1000PI/12.56 = 500/12.56
= 39.8Hz
14biii)
Speed (v) = F x Wave length
= V = F x Wave Length
V = 500/12.56 x 12.56‎
= 500cm/s
Conversation to M = 500/100
= 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=821n
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