Neco 2016 PHYSICS Obj And Theory Answers – May/July Expo

       

                                

NECO (PHYSICS) ANSWER

Physics OBJ:

1-10: BAEDEECDEB

11-20: CDADDDBCBB

21-30: DBEBBEADEB

31-40: ABEBCBCCDA

41-50: BDBCEDAAAE

51-60: AAABBACECA

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PHYSICS-ANS-BY-DONIZZY

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12ai)

centre of gravity of a body can be defined as a point on the body where the resultant weight of the body act

12aii)

C.G=centre of gravity

12b)

C.g = centre of gravity

:- v= u - gt

Of maximum height v=O - K

O= u-gt

For vertical component, U =uSin tita

Therefore O= usin tita- gt

gt =uSin tita

T=uSin tita/g

Where T is the time taken to maximum height

12c)

Taken moment about point A

Cwm = {60*10)+ (20*60)

Cwm=600+1200

Cwm=1800

Acwm = (20*40) + (R3 * 40)

Acwm=800+80R3

At equilibrium, Cwm=Acwm

1800=800+40r3

1800-800=40r3

1000=40r3

R3=1000/40

R3=25N

RA+RB=20+60+20

RA+25=100

RA=100-25

RA=75N

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15a)

electrical potential is the workdone in driving a unit charge of electric current from one point to another in a closed circuit. It is measured in volta(V)

15b)

A metal rod can be made into a magnet by divided touch me thod as shown in the diagram above.

The metal rod is stroke at the middle with opposite pole end of two permanent magnets towards the opposite ends several times opposite polarity are then formed

15ci)

VR=120v---->Vl=50v---->Vc=134.39v

220v,506z

15cii)

V^2=Vr^2+(Vl-Vc)^2

220^2=120^2+(50-Vc)^2

48400=14400+(50-Vc)^2

48400=14400=(50-Vc)^2

34000=(50-Vc)^2

50-Vc=sqr34000

50-Vc=184.39

-Vc=184.39-50

Vc=134.39v

;the potential difference acrross the capaitor is 134.39v

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9a)

i)by heating

ii)electrical method

9b)

energy stored=1/2CV^2

given that t

C=4HF =4*10^-6F

v=800v

=1/2*4*10^-6*800*800

=2*800*800*10^-6

=1280000j*10^-6

=1.28j

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13a)

dew point is the temperature at which the water vapour present in the atmosphere is just sufficent to saturate it

13b)

mist is formed as a result of condensed drops of moisture throughout the mass of cooled air. That is when water droplet in the air cool suddenly

13ci)

the plastic comb will acquire electric charges

13cii)

the plasic com can attract small pieces of paper due to the acquired charges

13di)

area expansivity(B)=2§

=2*1.2*10^-5

B=2.4*10^-5 1k

13dii)

given that initial length=6cm

initial area A=6*6=36cm^2

rise in temperature =25k

linear expansivity=1.2*10^-5/k

area expansivity =2.4*10^-5/k

new area At=Ao(1+Btita)

At=36(1+2.4*10^-5*25)

At=36(1+ 60*10^-5)

At=36(1+0.0006)

At=36(1.0006)

At=36.0216

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11)

Tabulate

-Hard Xray-

i)high penetrating power

ii)short wave length

iii)produce high voltage

-soft Xray-

i)low penetrating power

ii)long wave length

iii)produced at low voltage

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8a)

Electric current is the rate of charge flow past a given point in an electric circuit, measured in Coulombs/second which is named Amperes.

8b)

d=30cm,£=1.5*10^-5c r=30cm

30/100=0.3m

V=kE/r=9*10^9*1.5*10^-5/0.3

=13.5*10^4

=13.5*10^5/3

V=4.5*10^5

V=450kv

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5)

V1=700cm^3, T1=30dgree-census+273=303k, P1=606mmHg

V2=700-300=400cm^3, T2=47+273=320k

from general gas law

P1V1/T1 = P2V2/T2

606*700/303=P2*400/320

P2=606*700*320/303*400

P2=1120mmHg

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4a)

i)pulley

ii)the inclined plane

4b)

load------>fulcrum------>effort

eg-crowbar

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2a)

i)distance covered=5m+10m=15m

ii)magnitude of his displacement

=a^2=b^2+c^2

x^2=5^2+10^2=25+100

x^2=125

x=sqr125

=5sqr5m

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1ai)

i)Rockets are used for space travels.

ii)Rockets are used for launching satellites into space

1aii)

i)Artificial Satellites are used to send signals for televisions,radio, etc

ii)Artificial satellites they are used for monitoring cloud patterns for a weather station

1b)

A propeller like piece called turbine is been rotated continuously by falling water from a dam, which then turns a metal shaft in an electric generator,which is the motor that produces electricity

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14ai)

-Triangular prism,two convex lens,one white light bulb,white board

-Prism:for seperation of light into components

Convex lens:for focusing component colour bulb-for producing light

White board:for recieving components colours

14b)

Stationary waves are formed when two identical waves travelling in opposite directions meet and superimpose on each other while progressive waves are formed from energy which move forward in the direction of the waves

14c)

n=Sin1/2(A+D)/Sin1/2A

1.5=sin1/2(60+D)/sin1/2(60)

1.5=sin1/2(60+D)/sin(30)

1.5*0.5=sin1/2(60+D)

sin^-10.75=sin1/2(60+D)

1/2(60+D)=48.6

D=97.2-60

=37.2degrees

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16ai)

-Photocells convert the change in the intensity of light into electric current

-Photocells are used as light detectors

16aii)

-X-ray can cause cancer

-It leads to destruction of body cells and tissues

16b)

Gamma rays,X-rays and alpha rays

-Gamma rays,No magnetic effect

-X-rays-No magnetic effect

16ci)

Frequency =1.0*10^-15Hz

Work function=3.3*10^-19J

eVo=hF-W

h=6.6*10^-34Js, W=work function

f=1.0*10^-15Hz

eV=6.6*10^-34*1.0*10^-15-(3.3*10^-19)

eV=6.6*10^-49-3.3*10^-19

eV=-3.3*10^-19

Recall V=flanda

3.0*10^8=1*10^-15*landa

landa=3*10^23m

16cii)

Stopping potential(v)

eV=-3.3*10^-19

=>1.6*10^-19=-3.3*10^-19

e=1.6*10^-19

=>1.6*10^-19*e=-3.3*10^-19

e=-3.3*10^-19/1.6*10^-19

e=-2.0625

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17ai)

-Lenses are used for making spectacles which are used for correcting eye problems

-Lenses are used making microscopes which are used for magnifying objects

17aii)

-Plane mirrors are used for making periscope

-They are used for kaleidscope

17bi)

-Via heat energy

-Via eddy current

17ci)

Teleprescence is the use of virtual reality technology,especially for remote control of machinery or for apparent participation in distant events

17cii)

-Laboratories and conferences

17di)

Linear magnification=Image size/Object size

480/120=4

17dii)

m=v/f-1

4=120/f-1

4f=120-f

4f+f=120

5f=120

f=24cm

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