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2017 WAEC - PHYSICS ANSWERS

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Physics OBJ:
1-10: CAABADACC
11-20: BAADDCBADA
21-30: CCBAAACBAB
31-40: BCADDBBBAC
41-50: BCDAADABCA



TAKE NOTE OF THESE SYMBOLS AND UNDERSTAND THEM VERY WELL

(i) / means division or divide
Examples:
2/2 means 2/2 ie 2 over 2.
2 whole no 3/4 means 2¾
M=wp+(1/3)yp^2 means m=wp + ¾y2
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(ii) * means multiplication
Example: 2*2 means 2×2
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(iii) ^ means Raise to power
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(iv) Sqr root means √
Examples:
√3-√6+2√3 means Root 3-root6+2root 3
√(¾) means sqr root(3/4)
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PART A
(Answer only 5 questions)
(1)
PLS SKETCH.
-decrease in height (h)
-increase in time (t)
-this shows that distance changes with time

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(2)
given that U=15ms^-1
R=U* sqr2h/g
h=20m
g=10
R=15*sqr2*20/10
R=15*sqr40/10
R=15*sqr4
R=15*2=30m
R=30m

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(3)
(i)Brownian motion
(ii)Atomic size
(iii)Expansion

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(4)
L1=14cm F1=4N,F2=6N
L2=4cm, Lo=?
Using hooke's law
4/14-Lo*6/4-Lo
4(4-Lo)=6(14-Lo)
16-4Lo=64-6Lo
-4Lo+6Lo=64-16
2Lo=48
Lo=48/2
Lo=24Cm

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(5a)
(i)force
(ii)length

(5b) 
By increasing the density mosquitoes larvae than the density of water

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(6)
(i) Energy efficient - It is so far, the best light for interior lighting.
(ii) Low production cost (of tubes, not of the ballasts)
(iii) Long life of tubes

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(7)
(i) It is cheaper and quite easy to manufacture
(ii) It requires low voltage sources for it to function
(iii) It cannot be easily broken

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PART B
(Answer only 3 questions)
(8a)
(i) It is a straight line graph
(ii) The gradient is the velocity

(8b)
If their distance and masses are doubled their corresponding force would also be doubled and the work done respectively
I.e.Workdone=Force * distance
Force= Mass * Acceleration
W= Mg * d
|
Increase

(8c)
(i) Acceleration due to gravity
(ii) At maximum height, final velocity is zero

(8d)
(i)pushing someone on a swing.
(ii)Tuning a radio to a particular frequency.

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(11ai) 
A dielectric is an electrical insulator that can be polorised by an applied electric field.

(11aii)
Given that A = 9.6*10^-3M^2
d = 2.25*10^4
Eo = 8.85*10^-12 F/m
Er = 900
C = /
using; C = EoErA/d

Capacity, C = 8.85*10^-12*900*9.6*10^-3/2.25*106-4
C = 33984 * 10^-11
C = 3.3984 8 10^7 F
C =0.34#F

(11bii)
Combined resistance RT
RT= (400*400)/400+400 = (800*800)/(800+800)
RT= 200+400
RT =600 ohms
Current supplied by battery = v/RT
= 6/600
=0.01A

Voltage drop across 400 ohm resistors
= 200*0.01
=2v

Therefore the voltmeter reading is
= 6 - 2
= 4v

(11c)
Equivalent resistance is:
RT = 2+2 +(2*2)/2+2
RT = 4+1
RT = 5 ohms

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(12ai)
Nuclear fission is a nuclear reaction in which a heavy nucleus splits spontaneously or on impact with another particle, with the release of energy.

(12aii)
(a) 
A graphite reactor is a nuclear reactor that uses carbon as a neutron moderator, which allows un-enriched uranium to be used as nuclear fuel.

(b)
Boron rods are used in nuclear reactors to control the fission rate of uranium and plutonium. They are composed of chemical elements such as boron, silver, indium and cadmium that are capable of absorbing many neutrons without themselves fissioning.

(c)
Liquid sodium serves as coolant in a nuclear fission reactor.



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