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Physics
UTME / JAMB 2021
Heat and Temperature
Solution
A given mass of gas has a pressure of 80 Nm\(^{-2}\) at a temperature of 47 C. If the temperature is reduced to 27 C with volume remaining constant, the new pressure is?
A
46.0 Nm\(^{-2}\)
B
75.0 Nm\(^{-2}\)
C
80.0 Nm\(^{-2}\)
D
85.3 Nm\(^{-2}\)
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
Using \(\frac{P_{1}}{T_{1}} = \frac{P_{2}}{T_{2}}\)
\(P_1\) = 80Nm\(^{2}\)
\(T_1\) = 47 + 273 = 320k
\(T_2\) = 27 + 273 = 300k
\(P_2\)?
\(\therefore\) = \(P_2\) = \(\frac{P_{1}T_{2}}{T_{1}}\)
= \(\frac{80 \times 300}{320}\) = 75.Nm\(^{2}\)
Source: WAEC / JAMB / NECO Classroom Archive (Record #60611)
Physics
UTME / JAMB 2021
Heat and Temperature
Solution
A gas at a volume of V\(_{0}\) in a container at pressure p\(_{0}\) is compressed to one-fifth of its volume. What will be its pressure if the magnitude of its original temperature T is constant?
A
\(\frac{p_{0}} {5}\)
B
\(\frac{4p_{0}}{5}\)
C
\(p_0\)
D
5\(P_0\)
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
\(p_1\) = \(P_0\), \(V_1\) = \(V_0\), \(V_2\) = \(\frac{1}{5}\)\(V_0\) \(P_2\) = ?
\(P_1\)\(V_1\) = \(P_2\)\(V_2\)
\(P_2\) = \(\frac{P_{1}V_{1}}{V_{1}}\)
= \(\frac{\not P_{o}V_{o}}{\frac{1}{5}P_{o}}\) = 5\(\not P_{o}\)
Source: WAEC / JAMB / NECO Classroom Archive (Record #60776)
Physics
UTME / JAMB 2021
Measurement of Heat Energy
Solution
0.5kg of water at 10ºC is completely converted to ice at 0ºC by extracting (88000) of heat from it. If the specific heat capacity of water is 4200jkg\(^{1}\) Cº. Calculate the specific latent heat of fusion of ice.
A
9.0kjkg\(^{-1}\)
B
84.0kjkg\(^{-1}\)
C
134.0kjkg\(^{-1}\)
D
168.0kjkg\(^{-1}\)
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
Heat involved (H) = 88,000J, Mass(M)= 0.5kg, specific heat capacity of water(C) = 4200JkgºC,
Specific latent heat of fusion(L) = ?, Temperature change(\Delta\theta) = \theta2 - \theta1 = (10 - 0)^\circ = 10^\circ
H = MC\Delta\theta + ML
or
H = M(C\Delta\theta + L) -->\(\frac{H}{M}\) = C\Delta\theta + L
: L = \(\frac{H}{M}\) - C\Delta\theta = \(\frac{88,000}{0.5}\) - 4200 \(\times\) 10
L = 176,000 - 42000 = 134,000
L = 134,000 or 134kj/kg
Source: WAEC / JAMB / NECO Classroom Archive (Record #60731)
Physics
UTME / JAMB 2021
Measurement of Heat Energy
Solution
Calculate the heat energy required to vaporize 50g of water initially at 80ºC if the specific heat capacity of water is 4.23jg\(^{-1}\)k\(^{-1}\) (specific latent heat of vaporization of water is 2260jg\(^{-1}\)
A
530000J
B
23200J
C
17200J
D
130000J
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
H = mc\(\bigtriangleup\theta\) + mL
H = ?
m = 50g, c = 4.23J/gk,L = 2260, \(\bigtriangleup\theta\) = 80ºC
H = 50 [4.23 x 80 + 2260]
= 129920 \(\approx\) 130,000J
Source: WAEC / JAMB / NECO Classroom Archive (Record #60740)
Physics
UTME / JAMB 2021
Measurement of Heat Energy
Solution
A piece of substance of specific heat capacity 450Jkg\(^{-1}\)k\(^{1}\) falls through a vertical distance of 20m from rest. Calculate the rise in temperature of the substance on hitting the ground when all its energies are converted into heat. [g = 10ms\(^{-2}\)]
A
\(\frac{2}{9}\)ºC
B
\(\frac{4}{9}\)ºC
C
\(\frac{9}{2}\)ºC
D
\(\frac{9}{4}\)ºC
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
Using the law of conservation of energy
mc\(\bigtriangleup\theta\) = mgh
\(\bigtriangleup\theta\) = \(\frac{gh}{c} = \frac{10 \times 20}{450} = \frac{4}{9}\)ºC
Source: WAEC / JAMB / NECO Classroom Archive (Record #60777)
Physics
UTME / JAMB 2021
Evaporation and Boiling
Solution
Which of the following instruments may be used to measure relative humidity?
A
Hydrometer
B
Manometer
C
Hygrometer
D
Hypsometer
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
A hygrometer is an instrument that is used to measure water vapor in the atmosphere. This is also commonly referred to as relative humidity in the atmosphere.
Source: WAEC / JAMB / NECO Classroom Archive (Record #60733)
Physics
UTME / JAMB 2021
Evaporation and Boiling
Solution
I. A liquid boils when its saturated vapor pressure is equal to the external pressure
II. Dissolved substances in pure water lead to an increase in the boiling point.
III. When the external pressure is increased, the boiling point increases.
IV. Dissolved substances in pure water decreases the boiling point
Which of the above combinations are peculiarities of the boiling point of a liquid?
A
I, II and III only
B
I, II, III, and IV
C
I, II, and IV
D
II, III, and IV
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
The boiling point of a liquid depends on temperature, atmospheric pressure, and the vapor pressure of the liquid.
When the atmospheric pressure is equal to the vapor pressure of the liquid, boiling will begin
Source: WAEC / JAMB / NECO Classroom Archive (Record #60778)
Physics
UTME / JAMB 2021
Simple Ac Circuit
Solution
A 2H inductor has negligible resistance and is connected to a \(\frac{50}{\pi}\) Hz A.C supply. The reactance of the inductor is?
A
200\(\Omega\)
B
50\(\Omega\)
C
\(\frac{100}{\pi}\)
D
\(\frac{25}{\pi \Omega}\)
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
Given;
L = 2H
F = \(\frac{50}{\pi}\) \(H_2\)
\(X_L\) = ?
\(X_L\) = 2\(\pi\)fL = 2\(\pi\) x \(\frac{50}{\lambda}\) x 2
= 200\(\Omega\)
Source: WAEC / JAMB / NECO Classroom Archive (Record #60841)
Physics
UTME / JAMB 2021
Structure of the Atom
Solution
If the frequency of an emitted x-ray is 1.6 x 10\(^{16}\)Hz, the accelerating potential is?
[e = 1.6 x 10\(^{-19}\)J, h = 6.63 x 10-\(^{34}\)Js]
A
6630.0V
B
663.0V
C
66.3V
D
6.6V
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
Given f = 1.6 x10\(^{16}\)\(H_3\), h = 6.63 x 10\(^{-39}\)Js
e = 1.6 x 10\(^{-19}\)C, V = ?
V = \(\frac{w}{e} = \frac{hf}{e}\) = \(\frac{1.6 \times 10^{16} \times 6.63 \times 10^{34}}{1.6 \times 10^{-19}}\)
= 66.3V
Source: WAEC / JAMB / NECO Classroom Archive (Record #60745)
Physics
UTME / JAMB 2021
Structure of the Nucleus
Solution
A certain radioactive source emits radiation that was found to be deflected by both magnetic and electric fields. The radiation is?
A
beta rays
B
gamma rays
C
x-rays
D
ultra-violet rays
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
Both the electric field and magnetic field affect the \beta-particles.
Source: WAEC / JAMB / NECO Classroom Archive (Record #60749)
Physics
UTME / JAMB 2021
Refraction of Light
Solution
A man stands 4m in front of a plane mirror. If the mirror is moved 1m towards the man, the distance between him and his new image is?
A
3m
B
5m
C
6m
D
10m
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
Objects distance (u) = image distance (v)
object distance = 3m
|uv| = 3 + 3 = 6m
Source: WAEC / JAMB / NECO Classroom Archive (Record #60812)
Physics
UTME / JAMB 2021
Refraction of Light
Solution
The inside portion of part of a hollow metal sphere of diameter 20cm is polished. The portion will therefore form a?
A
concave mirror of focal length 5cm
B
concave mirror of focal length 10cm
C
convex mirror of focal length 5cm
D
convex mirror of focal length 10cm
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
Concave Mirror: It is a spherical mirror whose outer surface is polished and inner or concave side is reflecting surface.
Convex Mirror: It is a spherical mirror whose inner surface is polished and whose outer side or convex side is the reflecting surface.
f = \(\frac{m}{4}\) = f = \(\frac{d}{4}\)
f = \(\frac{20}{4}\) = 5cm
(For metal, it is the polished side that will be the reflecting surface)
Source: WAEC / JAMB / NECO Classroom Archive (Record #60819)
Physics
UTME / JAMB 2021
Refraction of Light
Solution
The velocities of light in air and glass are 3.0 x 10\(^8\)ms\(^{-1}\) and 2.0 x 10\(^8\)ms\(^{-1}\) respectively. If the angle of refraction is 30º, the sine of the angle of incidence is?
A
0.33
B
0.50
C
0.67
D
0.75
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
\(\frac{\text {sin i}}{\text {sin r}}\) = \(\frac{\text {velocity in air}}{\text {velocity in glass}}\)
\(\frac{\text {sin i}}{\text {sin 30}}\) = \(\frac{3 \times 10^{8}}{2 \times 10^{8}}\)
Sin i = \(\frac{3}{4}\) = 0.75
Source: WAEC / JAMB / NECO Classroom Archive (Record #60827)
Physics
UTME / JAMB 2021
Waves
Solution
The equation of a wave traveling along the positive x-direction is given by; y = 0.25 x 10\(^{-3}\) sin (500t - 0.025x). Determine the angular velocity of the wave motion.
A
0.25 x 10\(^{-3}\)rads\(^{-1}\)
B
0.25 x 10\(^{-1}\)rads\(^{-1}\)
C
5.00 x 10\(^{2}\)rads\(^{-1}\)
D
2.50 x 10\(^{3}\)rads\(^{-1}\)
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
Using y = A sin (wt + 0)
Given y = 0.25 x 10\(^{-3}\)sin (500t - 0.025x)
By comparing, w = 5.00 x 10\(^{2}\)rads\(^{-1}\)
Source: WAEC / JAMB / NECO Classroom Archive (Record #60795)
Physics
UTME / JAMB 2021
Sound Wave
Solution
A source of sound produces waves in air of wavelength 1.65m. If the speed of sound in air is 330ms\(^{-1}\), the period of vibration in air is?
A
200
B
0.005
C
0.5
D
0.02
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
V = \(\frac{\lambda}{T}\)
: v = 330ms\(^{-1}\)
\(\lambda\) = 1.65m
T = ?
330 = 1.65
T = \(\frac{1.65}{330}\) = 0.005s
Source: WAEC / JAMB / NECO Classroom Archive (Record #60734)