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Physics
WAEC / WASSCE 2000
Atomic, Quantum, Nuclear Physics & Electronics
Solution
A nuclide \(^{202}_{84} Y\) emits in succession an \(\alpha-particle\) and a \(\beta-particle\). The atomic number of the resulting nuclide is
A
198
B
83
C
82
D
80
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
\(^{202}_{84} Y\) → \(^4_2\)He + \(^0_{-1}\)e + \(^{98}_{83}\)X
Therefore, the atomic number of the resulting nuclide = 83.
Source: Myschool Past Questions Archive (Record #33849)
Physics
WAEC / WASSCE 2000
Atomic, Quantum, Nuclear Physics & Electronics
Solution
The half life of a radioactive substance is 14 days. If 48g of this substance is stored, after how many days will 1.5g of the original substance remain?
A
84 days
B
70 days
C
56 days
D
40 days
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
Using N = N\(_o\)\((\frac{1}{2})^n\)
N\(_o\) = 48g, N =1.5g and n = number of half-lives
1.5 = 48\((\frac{1}{2})^n\)
\(\frac{1.5}{48}\) = \(\frac{1}{32}\) = (\(\frac{1}{2})^5\) = \((\frac{1}{2})^n\)
n = 5 (same base, equate power)
Total time = n x t\(_{\frac{1}{2}}\) = 5 x 14 = 70 days
Therefore, 1.5g will remain after 70 days.
Source: Myschool Past Questions Archive (Record #33851)
Physics
WAEC / WASSCE 2000
Current Electricity & Electric Circuits
Solution
A material of mass 1.0 x 10\(^{-2}\)kg undergoes a fission process which decreases its mass by 0.02 percent. Calculate the amount of energy released in the process. (c = 3.0 x 10\(^{8}\)ms\(^{-1}\))
A
1.8 x 1020J
B
1.8 x 1013J
C
1.8 x 1011J
D
1.8 x 1010J
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
To calculate the energy released during the fission process, we can use Einstein's mass-energy equivalence principle, given by the formula:
E = \Deltamc\(^2\)
m = 1.0 x 10\(^{-2}\)kg
c = 3.0 x 10\(^8\)ms\(^{-1}\)
Mass decrease = 0.02%
\Deltam = 0.02% x 1.0 x 10\(^{-2}\) = 2.0\times10\(^{−6}\)kg
E = \Deltamc\(^2\) = 2.0\times10\(^{−6}\) x (3.0 x 10\(^8\))\(^2\) = 1.8\times10\(^{11}\)J
Source: Myschool Past Questions Archive (Record #33856)
Physics
WAEC / WASSCE 2000
Atomic, Quantum, Nuclear Physics & Electronics
Solution
Absorption line spectra exhibited by atoms is a result of
A
change in the kinetic energy of a movimg atom
B
instability of the nucleons
C
excitation of an electron in the atom
D
transition of an electron from a higher to a lower energy level
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
Absorption line spectra are produced when electrons in an atom absorb specific wavelengths of light to move from a lower energy level to a higher energy level (excitation). The absorbed energy corresponds to the difference in energy between the two levels, resulting in dark lines in the spectrum at those specific wavelengths.
Source: Myschool Past Questions Archive (Record #33858)
Physics
WAEC / WASSCE 2000
Current Electricity & Electric Circuits
Solution
In a nuclear reactor, electricity can be generated through the following processes. Arrange the processes in the correct order. i. The steam is used to drive turbines. ii. The heat energy released is removed by passing water through the reactor. iii. The turbines in turn generate electricity. iv. The water then passes through some form of heat exchanger to produce steam
A
ii, iv, i and iii
B
i, ii, iii and iv
C
iii, i, iv and ii
D
iv, i, iii and ii
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
To arrange the processes in the correct order for generating electricity in a nuclear reactor, let's break down the steps involved:
1. Heat Generation: The nuclear reaction generates heat.
2. Heat Removal: This heat is removed by passing water through the reactor.
3. Steam Production: The heated water then passes through a heat exchanger to produce steam.
4. Turbine Operation: The steam drives turbines.
5. Electricity Generation: The turbines generate electricity
Therefore, the correct order is:
ii: The heat energy released is removed by passing water through the reactor.
iv: The water then passes through some form of heat exchanger to produce steam.
i: The steam is used to drive turbines.
iii: The turbines in turn generate electricity
Source: Myschool Past Questions Archive (Record #33949)
Physics
WAEC / WASSCE 2000
Atomic, Quantum, Nuclear Physics & Electronics
Solution
The duality of matter implies that matter
A
exists as a particle of dual composition
B
has momentum and energy
C
has both wave and particle properties
D
is made up of dual materials
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
The duality of matter refers to the concept in quantum mechanics that matter exhibits both wave-like and particle-like properties.
Source: Myschool Past Questions Archive (Record #33951)
Physics
WAEC / WASSCE 2000
Atomic, Quantum, Nuclear Physics & Electronics
Solution
In which of the following transitions is the largest quantum of energy liberated by an hydrogen atom when the electron changes energy levels? [n is the quantum number]
A
n = 2 to n = 1
B
n = 1 to n = 2
C
n = 2 to n = 3
D
n = 3 to n = 2
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
The largest quantum of energy a hydrogen atom liberates occurs during a transition from a higher to a lower energy level. The energy difference between levels can be calculated using the formula:
E = −13.6eV(\(\frac{1}{n_f^2} - \frac{1}{n_i^2}\))
n\(_i\) is the initial quantum number (higher energy level),
n\(_f\) is the final quantum number (lower energy level.
A. n = 2 to n = 1
Source: Myschool Past Questions Archive (Record #33943)
Physics
WAEC / WASSCE 2000
Waves, Sound & Vibrations
Solution
A proton of wavelength \(\lambda_o\) is emitted when an electron in an atom makes a transition from a level of energy 2E. If the electron transits from \(\frac{4}{3}E_k\) to E level, determine the wavelength of the photon that would be emitted
A
3\(\lambda_o\)
B
2\(\lambda_o\)
C
\(\frac{3}{4}\)\(\lambda_o\)
D
\(\frac{1}{3}\)\(\lambda_o\)
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
2E - E = \(\frac{hc}{\lambda}\) = E = \(\frac{hc}{\lambda}\)
\(\frac{4}{3}\)E = \(\frac{hc}{\lambda_{new}}\)
E = \(\frac{3hc}{\lambda_2}\)
\(\frac{3hc}{\lambda_2}\) = \(\frac{hc}{\lambda}\)
\(\lambda_{new}\) = 3 \(\lambda_o\)
Source: Myschool Past Questions Archive (Record #33945)
Physics
WAEC / WASSCE 2000
Current Electricity & Electric Circuits
Solution
The nucleon number and the proton number of a neutral atom of an element are 23 and 11 respectively. How many neutrons are present in the atom?
A
11
B
12
C
23
D
34
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
Nucleon number = Proton number + Neutron number
Neutron number = Nucleon number − Proton number
Neutron number = 23 - 11 = 12
The number of neutrons present in the atom is 12
Source: Myschool Past Questions Archive (Record #33947)
Physics
WAEC / WASSCE 2000
Current Electricity & Electric Circuits
Solution
Measure and record the e.m.f. of the accumulator provided.
Connect a circuit as shown in the diagram. S is a standard resistor and R is a resistance box.
With R = 0\(\Omega\), close the key K. Read and record the ammeter reading I. Evaluate 1\(^{-1}\).
Repeat the procedure for R=1,2, 3, 4, and 5\(\Omega\). Tabulate your readings.
Plot a graph of R on the vertical axis and 1\(^{-1}\) on the horizontal axis, starting both axis from the origin (0,0).
Determine the slope s of the graph and find the intercept C on the vertical axis.
State two precautions taken to ensure accurate results.
(b)i. State two advantages of a lead-acid accumulator over a Leclanche cell.
ii. A parallel combination of 3\(\Omega\) and 4\(\Omega\) resistors is connected in series with a resistor of 4\(\Omega\) and a battery of negligible internal resistance. Calculate the effective resistance in the circuit.
A
11
B
12
C
23
D
34
E
mutual forces excerted by the balls
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
The e.m.f of the accumulator = 1.5v
Table of value/observations
R(\(\Omega\))
1\(_{amp}\)
1\(^{-1}_{amp}\)
0
0.78
1.28
1
0.50
2.00
2
0.38
2.63
3
0.30
3.33
4
0.25
4.00
5
0.22
4.55
Slope (s) = \(\frac{y_{2}-y_{1}}{x_{2}-x_{1}} = \frac{4-1}{4-2} = \frac{3}{2}\)
The intercept on the vertical axis is =-1.85\(\Omega\)
Precautions:
I tightened connections.
I avoided errors due to parallax in reading ammeter or voltmeter.
I noted zero error of ammeter/ voltmeter.
I removed key when readings were not taken.
I took repeated readings from the table, i.e. averaging the reading.
(b)i.
- The lead-acid accumulator can be recharged while the Leclanche cell cannot.
- The lead-acid accumulator has the capacity to supply large currents for a long time while the leclanche cell does not.
ii. The two resistors 3\(\Omega\) and 4\(\Omega\) are connected in parallel.
\(\therefore\) The equivalent resistance (\(\Omega\) = \(\frac{1}{R} = \frac{1}{3} = \frac{1}{4} = \frac{4+3}{12}\)
= \(\frac{7}{12}\) = 1.71
The effective resistance in the circuit = 1.71 + 4 = 5.71\(\Omega\)
Source: Official Exam / Past Question Archive
Physics
UTME / JAMB 2000
Scalars, Vectors & Relative Motion
Solution
A handbag containing some load weighing 162N is carried by two students each holding the handle of the bag next to him. If each handle is pulled \( 60^{\circ} \) to the vertical, find the force on each student's arm
A
81N
B
121N
C
162N
D
324N
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
Weight of handbag(W) = 162N acting vertically downward
Angle of pull (\(\theta\)) = 60º to the vertical
Since the handbag is in equilibrium, the total vertical force must equal the weight of the handbag.
Let F be the force exerted by each student on the handle. The vertical component of the force from each student is given by:
Fv = F cos 60º but there are two students
2Fcos60º = 162
2F(0.5) = 162 ( cos60º = 0.5)
F = 162 ( since 2 x 0.5 = 1)
Therefore, the force exerted by each student on the handbag is: 162N
Source: Myschool Past Questions Archive (Record #41496)
Physics
NECO SSCE 2000
Magnetism, Electromagnetism & AC Circuits
Solution
A particle of charge q and mass m moving with a velocity v enters a uniform magnetic field B in the direction of the field. The force on the particle is
A
Bqv
B
Bq\(\frac{v}{m}\)
C
Bqvm
D
mv\(\frac{B}{q}\)
E
\(\frac{mv}{Bq}\)
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
The formula for Force on the particle is Bqv.
Source: Myschool Past Questions Archive (Record #42674)
Physics
NECO SSCE 2000
Current Electricity & Electric Circuits
Solution
The helium isotope \(^3_2He\)
A
has three pro tons and two neutrons
B
has two protons and one neutron
C
has two protons and three neutrons
D
has one proton and two neutrons
E
cannot exist because it has the same mass number as tritium
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
Based on nuclear physics, the correct answer is B: \(^3_2\)He has two protons and one neutron.
Source: Myschool Past Questions Archive (Record #42682)
Physics
NECO SSCE 2000
Atomic, Quantum, Nuclear Physics & Electronics
Solution
When a metal is heated to a high temperature, electrons are emitted from its surface. The process is known as
A
photoelectric effect
B
thermionic emission
C
field emission
D
secondary emission
E
radioactive emission
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
The process by which free electrons are emitted from the surface of a metal when external heat energy is applied is called thermionic emission.
Source: Myschool Past Questions Archive (Record #42683)
Physics
NECO SSCE 2000
Current Electricity & Electric Circuits
A piece of stone weights 180 N in air and 150 N in a beaker containing 160 N of methylated spirit. What is the up thrust exerted on the stone?
A
50N
B
40N
C
30N
D
20N
E
10N
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #42684)