NABTEB 2021 Physics Obj & Essay Questions And Answers – May/june

*PHYSICS-ANSWERS*

Physics Obj
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THEORY
(1a)
Simple harmonic motion is the motion of a body whose acceleration is always directed towards a fixed point and is (directly) proportional to the displacement from the fixed point

(1bi)
Period : it is the time taken to complete one cycle of oscillation or vibration.
T=t/n

(ii)Frequency: It’s the number of complete oscillation per second.
F=n/t

(iii)Linear Velocity : It is the rate change of displacement with respect of time.
V=Wr
V= W√A² – x²

(iv)Angular Velocity : it’s the rate of change of angular of displacement
W= V/r

(1c)
λ¹/T¹= λ²/T²
0.8/2 =0.6/T²
T²=2*0.6/0.8
T²=1.5secs
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(2ai)
latent heat of fusion can be defined as a substance of a quantity of heat q required change a unit mass m of the substance at its melting point to a liquid without a change in temperature.

(2aii)
latent heat of vapourization is a substance which it’s quantity of heat q required to change a unit mass (m) of the substance from liquid at its boiling point to vapour without a corresponding change in temperature.

(2b)
[img]https://i.imgur.com/2aWAEfm.jpg[/img]

(2c)
original temp, ∅, = 0°c.
cubic expansivity, y = 5.7 x 10^-5k^-1 final temperature, ∅2 = 30°c original volume , v1
density = mass/volume
so therefore volume (v1) = mass/density
v1 = 170/8.53 x 10³
v1 = 0.02m³
y = ∆v/v1(∅2 -∅1)
∆v =y x v1(∅2 – ∅1)
∆v= 5.7 x 10^-5 x 0.02 x (30 – 0)
∆v= 3.42 x 10^-5m³
=3.42 x 10^-5m³
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(4ai)
The internal resistance of a cell is the opposition to current flow offered by the cell when it is discharging current to a circuit.

(4aii)
(a) An electric field is define as the region of space where a charge body experience an electric force.
(b) Electric line of force is an imaginary line drawn in an electric field in such a way that the direction at any point or the direction of the tangent.
(c) Uniform Field is the type of Field in which the lines (Field line) are straight
(d) Variable field is the type of Field in which the lines of Field are curred.

(4b)
[img]https://i.imgur.com/efRsDym.jpg[/img]

(4c)
Current flowing in the circuit
I = E/R+ r = 15/3 + r
P.d across cell,
V= E-V
V= 1.5 – 0.9
V= 0.6V
V= ir
ir= 0.6

I= 1.5/3+r
V= It
0.6 = 1.5/3+r x r
Cross multiply
1.5r= 0.6(3+r)
1.5r= 1.8 + 0.6r
1.5r – 0.6r = 1.8
0.9r= 1.8
r= 1.8/0.9= 2π
Final answer = 2π
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(5ai)
the number of proton in an atom also called atomic number.

(5aii)
The nucleon number (or mass number) of an atom is the total number of protons and neutrons it contains. The nucleon number of an atom is never smaller than the proton number.

(5aiii)
isotopes are atoms of the same element having the same atomic number but different mass number because of the difference in neutron number.

(5b)
The inherent radioactivity of uranium will then release a neutron, which will bombard another atom of 235U to produce the unstable uranium-236, which undergoes fission, releases further neutrons, and continues the process.The uranium atom can split any one of dozens of different ways, as long as the atomic weights add up to 236 (uranium plus the extra neutron). The following equation shows one possible split, namely into strontium-95 (95Sr), xenon-139 (139Xe), and two neutrons (n), plus energy

(5ci)
The electrons surrounding an atom are located in regions around the nucleus called “energy levels”. An energy level represents the 3-dimensional space surrounding the nucleus where electrons are most likely to be. The first energy level is closest to the nucleus.

(5cii)
λR=6•563°A
λB=4•861°A
1A=10^-¹⁰m
ER=hc/λr=6.6*10^-³⁴*3*10⁸/6.563*10^-¹⁰
=3.02*10^-16J

EB=hc/λB=6.6*10^³² * 3*10⁸/4.861*10^-¹⁰
=4.07*10^-¹⁶J

DE=EB=ER
=4.07*10¹⁶-3.02*10¹⁶
=1.05*10^-¹⁶J
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COMPLETED
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