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Physics
WAEC / WASSCE 2018
Mechanics and Properties of Matter
Solution
(a) Define binding energy in an atom.
(b) List three evidence to support the claim that X-rays are electromagnetic waves.
(c) List three peaceful uses of nuclear energy.
(d) Light of wavelength 4.5 x 10\(^{-7}\) in is incident on a metal resulting in the emission of photo electrons. If the work function of the metal is 3.0 x 10\(^{-9}\) J, calculate the:
(i) frequency of the incident light;
(ii) energy of the incident light;
(iii) energy of the photoelectrons. [Speed of light = 3.0 x 10\(^8\) ms\(^{-1}\), h = 6.6 x 10\(^{-34}\) Js]
medium Difficulty
Verified Correct Answer: Option
Physical Principles & Numerical Solution
(a) Binding energy is the minimum energy required to seperate the nucleus of an atom.
(b) Three evidences in support of the claim that x -rays are electromagnetic waves are:
(i) They can be polarized.
(ii) They can travel through a vacuum.
(iii) They travel with the speed of light.
(iv) They are not affected by electric field.
(v) They are not affected by magnetic field.
(c) Three peaceful uses of nuclear energy are:
(i) It is used in the treatment of tumour.
(ii) It is used to power submarines.
(iii) It is used to generate electricity.
(d) (1) c = f\(\lambda\) or f = \(\frac{c}{\lambda}\)
f = \(\frac{3.0 \times 10^8}{4.5 \times 10^{-7}}\)
f = 6.67 x10\(^{14}\)Hz
(ii) E = hf
= 6.67 x10\(^{-34}\) x 6.67 x10\(^{14}\)J
= 4.4 x10\(^{-19}\)J
(iii) K.E = E- W
= 4.4 x 10\(^{-19}\)
=1.4 x 10\(^{-19}\) - 3.0 x 10\(^{-19}\)
=1.4 x 10\(^{-19}\)J
Source: Myschool Past Questions Archive (Record #52874)
Physics
WAEC / WASSCE 2018
Mechanics and Properties of Matter
Diagram
Solution
You are provided with a pendulum bob, a metre rule, a stopwatch, a retort stand with clamp, and other necessary apparatus.
i. Suspend the pendulum bob from the clamp as illustrated in the diagram.
ii. Adjust the pendulum such that AC=L= 90 cm
iii. Displace the pendulum bob slightly such that it oscillates in a vertical plane.
iv. Measure and record the time t for 20 complete oscillations.
v. Evaluate T and \(\sqrt L\)
vi.Repeat the procedure for four others values of L= 80 cm,70 cm, 60 cm, and 50cm.
vii. Tabulate your readings
viii. Plot a graph with T on the vertical axis and \(\sqrt L\) on the horizontal axis.
ix. Determine the slope, s, of the graph.
x. Evaluate g= \(\frac{4\pi^{2}}{5^{2}}\)
xi. State two precautions taken to ensure accurate results.
(b) i. Determine from your graph, the period of the pendulum for L= 75 cm.
ii. A simple pendulum bob is set into simple harmonic motion. Sketch a diagram of the setup and indicate on it; the positions of:
(a) maximum velocity.
(b) maximum acceleration of the bob
Attached Figure / Diagram
medium Difficulty
Verified Correct Answer: Option
Physical Principles & Numerical Solution
S/N
L(cm)
t(s)
T = \(\overline{20}\)(S)
\(\sqrt L\)
1
90
38
1.90
9.49
2
80
36
1.80
8.94
3
70
34
1.70
8.37
4
60
32
1.50
7.73
5
50
30
1.50
7.07
viii. Scale: 2cm rep 0.05 unit on y-axis
2cm rep 1.0 unit on x-axis
ix. Slopes(s) = \(\frac{X_2 - X_1}{Y_2 - Y_1}\)
= (\(\frac{9.9 - 5.7}{2.0 - 1.25}\))
= \(\frac{4.2}{0.75}\)
= 5.6cm
x. Evaluate g = \(\frac{4\pi{^2}}{5^{2}}\)
= \(\frac{4(3.143)^{2}}{(5.6)^{2}}\)
= \(\frac{9.878}{31.36}\)
= 0.315
xi. Precuations:
i. Avoided zero error on stop clock/ metre rule.
ii. Avoided draught.
iii. Avoided conical oscillation
iv. Ensured that support was rigid or firm
v. Ensured bob/pendulum was free from table.
(b)i. \(\sqrt{75cm}\) = 8.66
ii.
Source: Myschool Past Questions Archive (Record #59880)
Physics
UTME / JAMB 2017
Mechanics and Properties of Matter
Solution
Calculate the upthrust on an object of volume 50cm3 which is immersed in liquid of density \(10^{3}\) kgm-3 [g = 10ms-2]
A
0.8N
B
2.5N
C
0.5N
D
1.0N
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
Upthrust = change in weight
density = \(\frac{\text{mass}}{\text{volume}}\)
Mass of liquid displaced = Density of Liquid \times Volume;
= \(10^{3} \times 50 \times 10^{−6}m^{3}\)
= 0.05kg
(Note that the volume of \(50cm^{3}\) was converted to \(m^{3}\) by multiplying by \(10^{6}\)) i.e \(50cm^{3} = 50 \times 10^{−6}m^{3}\)
Since mass displaced = 0.05kg
Upthrust = mg = 0.05 \times 10
= 0.5N
Source: Myschool Past Questions Archive (Record #46378)
Physics
UTME / JAMB 2017
Mechanics and Properties of Matter
Solution
Under what conditions are cathode rays produced in a discharge tube?
A
High pressure and low voltage
B
High pressure and high voltage
C
Low pressure and low voltage
D
Low pressure and high volatge
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
Cathode rays are produced in a discharge tube under Low pressure and high voltage
Source: Myschool Past Questions Archive (Record #46379)
Physics
UTME / JAMB 2017
Mechanics and Properties of Matter
Solution
Under which of the following conditions is workdone
A
A man supports a heavy food above his head with his hands
B
A boy climbs onto a table
C
A man pushes unto a table
D
A woman holds a pot of water
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
For work to be done, distance must be involved because
workdone = force × distance
Source: Myschool Past Questions Archive (Record #46380)
Physics
UTME / JAMB 2017
Mechanics and Properties of Matter
Solution
Calculate the specific latent heat of vaporization of steam of 1.13 x 10\(^6\)J of heat energy is required to convert 15kg of steam to water.
A
7.53 x 105 Jkg\(^{-1}\)
B
7.53 x 10-2Jkg\(^{-1}\)
C
\(7.53 \times 10^{4}\)Jkg\(^{-1}\)
D
7.53 x 10-3Jkg\(^{-1}\)
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
Quantity of heat = mass(m) \times specific latent heat (L)
Q = mL
L = \(\frac{Q}{m}\)
= \(\frac{1.13 \times 10^{6}}{15}\)
= \(7.53 \times 10^{4}\)Jkg\(^{-1}\)
Source: Myschool Past Questions Archive (Record #46383)
Physics
UTME / JAMB 2017
Mechanics and Properties of Matter
Solution
Which of the following instruments helps to maintain the correct humidity and temperature of a building?
A
A compressor
B
A refrigerator
C
Air blower
D
Air conditioner
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
Compressor is an instrument to supply air or other gas at increased pressure
Refrigerator is an appliance to keep things cold
Air blower is used to release air
Air conditioner is used to remove heat and maintain a stable temperature in an occupied space
Source: Myschool Past Questions Archive (Record #46391)
Physics
UTME / JAMB 2017
Mechanics and Properties of Matter
Solution
The S.I unit of moment of a force is
A
kgm
B
Nm
C
Jm
D
µm\(^{-1}\)
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
Moment of a force is the product of a force and the perpendicular distance from the line of action of the force
Moment = force \times distance
= N \times m
= Nm
Source: Myschool Past Questions Archive (Record #46394)
Physics
UTME / JAMB 2017
Mechanics and Properties of Matter
Solution
The instrument used to measure the pressure of a gas is
A
barometer
B
thermometer
C
hydrometer
D
manometer
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
Barometer is used to measure atmosphere pressure
Thermometer is used to measure temperature
Hydrometer is used to measure relative density of a liquid
Manometer is used to measure the pressure of a gas
Source: Myschool Past Questions Archive (Record #46401)
Physics
UTME / JAMB 2017
Mechanics and Properties of Matter
Solution
A man of mass 50kg ascends a flight of stains 5m high in 5 seconds. If acceleration due to gravity is 10ms\(^{-2}\) the power expended is
A
100w
B
200w
C
400w
D
500w
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
Power is the time rate of doing work
i.e power = \(\frac{\text{energy}}{\text{time}}\)
Since energy = mgH
∴ power = \(\frac{mgH}{t}\)
= \(\frac{50 \times 10 \times 5}{t}\)
= 500W
Source: Myschool Past Questions Archive (Record #46402)
Physics
UTME / JAMB 2017
Mechanics and Properties of Matter
Solution
Determine the focal length of a thin converging lens if the power is 5.0 dioptres
A
0.1 m
B
0.2 m
C
2.0 m
D
2.5 m
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
Power of a lens = \(\frac{1}{f}\)
f = focal length
f = \(\frac{1}{p}\)
= \(\frac{1}{5}\)
= 0.2m
Source: Myschool Past Questions Archive (Record #46405)
Physics
UTME / JAMB 2017
Mechanics and Properties of Matter
Solution
A string of length 5cm is extended by 0.04m when a load of 0.8kg is suspended at the end. How far will it extend if a force of 16N is applied? [g = 10ms\(^{-2}\)]
A
0.04m
B
0.12m
C
0.01m
D
0.08m
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
From Hoke's Law, F = ke, K = Constant of Force
For he first case, Force = mg,
= 0.8 × 10 = 8N
∴ 8 = k × 0.04
k = \(\frac{8}{0.04}\)
= \(\frac{200N}{m}\)
Since K is constant
For the second case, F = ke
F = 200 × e
∴ e = \(\frac{F}{200}\)
= \(\frac{16}{200}\)
= 0.08m
Source: Myschool Past Questions Archive (Record #46406)
Physics
UTME / JAMB 2017
Mechanics and Properties of Matter
Solution
How can energy loss be minimized through Eddy-current?
A
By using high resistance wire
B
By using insulated soft iron wires
C
By using low resistance wires
D
Bu using turns of wires
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
Eddy currents are produced by the varying flux cathode, the iron core of an equipment thus reducing efficiency due to power consumption. It can be reduced by laminating the core by breaking up the path of eddy current or by increasing the resistance of the core
Usage of insulated soft iron wire is to reduce hysteresis loss
Usage of low resistance wire (thick wire) is to reduce I2R loss
Usage of thick wire is to reduce leakage heat loss due to leakage of magnetic flux
Thus the correct answer is to use high resistance wire or thin wire
Source: Myschool Past Questions Archive (Record #46407)
Physics
UTME / JAMB 2017
Mechanics and Properties of Matter
Diagram
Solution
From the diagram above, calculate the energy stored in the capacitor
Attached Figure / Diagram
A
4.0 x 10\(^{-2}\)J
B
4.0 x 10\(^{-4}\)J
C
8.0 x 10\(^{-4}\)J
D
8.0 x 10\(^{-2}\)J
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
c = 8µF, v = 10v
Energy stored = \(\frac{1}{2}\) cv2
= \(\frac{1}{2}\) × (8 × 10− 6) × 102
= 4 × 10\(^{-4}\)
Source: Myschool Past Questions Archive (Record #46408)
Physics
UTME / JAMB 2017
Mechanics and Properties of Matter
Solution
A constant force of 5N acts for 5 seconds on a mass of 5kg initially at rest. Calculate the final momentum
A
125kgms−1
B
25kgms−1
C
15kgms−1
D
0kgms−1
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
Impulse = momentum
Impulse = Force (f) \times time (t)
Momentum = mass (m) \times velocity (v)
∴ Ft = Final momentum - initial momentum
FT = mv - mu
Since it is initially at rest u = 0
∴ 5 \times 5 = mv − m(0)
25 = mv
∴ Final momentum = 25kgms\(^{-1}\)
Source: Myschool Past Questions Archive (Record #46409)