Welcome to our WAEC past question and answer series. In this post, we will be sharing Physics 2017 past questions and answers. Stay tuned enjoy while learning.
1. Which is the incorrect formula for a body accelerating uniformly?
2. Which of the following is not an electromagnetic radiation?
Solution
Electromagnetic waves do not require any material medium, but sound waves is a mechanical wave that require a material medium
3. Calculate the electric field intensity between two plates of potential difference 6.5V when separated by a distance of 35cm.
Solution
Electric Field Intensity (E) = vd
= potential difference/distance
= 6.5v/35cm
= 6.5/35×10−2
= 18.57NC-1
4. Why do soldiers march disorderly while crossing a bridge?
Solution
Soldiers march disorderly while crossing a bridge to prevent resonance because when soldiers march in orderly manner across a bridge, they generate a rhythmic oscillation of wave out. The bridge and at a certain point, would start oscillation to the same rhym as that of the marching steps. This oscillation would reach a maximum peak when the bridge can no longer sustain its own strength and hence collapses. So for this reasons, soldier are ordered to march disorderly while crossing a bridge
5. Calculate the upthrust on an object of volume 50cm3 which is immersed in liquid of density 103kgm-3 [g = 10ms-2]
Solution
Upthrust = change in weight
density = mass/volume
Mass of liquid displaced = Density of Liquid × Volume;
= 103 × 50 × 10− 6m3
= 0.05kg
(Note that the volume of 50cm3 was converted to m3 by multiplying by 106) i.e 50cm3 = 50 × 10−6m3)
Since mass displaced = 0.05kg
Upthrust = mg = 0.05 × 10
= 0.5N
6. Under what conditions are cathode rays produced in a discharge tube?
Solution
Cathode rays are produced in a discharge tube under Low pressure and high voltage
7. Under which of the following conditions is workdone
Solution
For work to be done, distance must be involved because
workdone = force × distance
8. Calculate the specific latent heat of vaporization of steam of 1.13 x 106J pf heat energy is required to convert 15kg of it to water.
Ans: C
Solution
Latent Energy = mass(m) × specific latent heat (L)
ε = mL
L = ε/mE/m
= 1.13×10615
= 7.53 × 104Jkg-1
9. A cell of internal resistance 2 π supplies current to a 6 π resistor. The efficiency of the cell is
Ans: C
Solution
Internal resistance determine the maximum current that can be supplied
Efficiency = rR × 100
= \frca26 × 100
= 33.3%
10. Which of the following statements is NOT correct?
Solution
Molecules of liquid are not stationary
Brownian motion is an evidence of particle nature of matter
matter is made up of molecules
The molecules of matter are in constant motion
11. A block and tackle pulley arrangement has 6 pulleys in which an effort of 50N supports a load of 200N, calculate the efficiency of the machine
Ans: C
Solution
Efficiency = maV.R x 1001
V.R = number of pulleys = 6
ma = LoadEffort = 20050 = 4
Effiecieny = 46 × 100 = 66.67%
Ans: A
Solution
Resistor connected in a parallel have an equivalence given by
1Reff = 13 + 13 + 13
= 1+1+13 = 33 = 1
Reff = 1ω
13. Which of the following instruments helps to maintain the correct humidity and temperature of a building?
Ans: D
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
14. An element and its isotope only differ in the number of
Ans: D
Solution
Isotopy is due to difference in mass number, what causes the difference is the difference in the number of neutrons present
15. The thermal expansion of a solid is an advantage in
Ans: A
Solution
Thermal expansion of a solid is majorly advantageous in the use of bimetallic strip in the balance of a watch so as not to lose time
16. The S.I unit of moment of a force is
Ans: B
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 × distance
= N × m
= Nm
17. A block and tackle pulley arrangement has 6 pulleys in which an effort of 50N supports a load of 200N, calculate the efficiency of the machine
Ans: C
No further explanations yet…
Ans: D
Solution
Magnification = Length of cameradistance of object from pin hole
m = 1260
= 0.2
Also magnification m = Height of imageHeight of object
∴ Height of image = m × height of object
= 0.2 × 70
= 14cm
19. When two objects P and Q are supplied with the same quantity of heat, the temperature change in P is observed to be twice that of Q. The mass of P is half that of Q. The ratio of the specific heat capacity pf P to Q is
Ans: C
Solution
H = mcθ
HP = HQ, θP = 2θ,
mP = 12mQ
∴ HP = mQCPθP, also HQ = mQCQθQ
Since HP = HQ
∴ mPcPθP = mQcPθq
Putting in the conditions
12mQ × cP × 2θQ = mQ × θQ × cQ
∴ cP = cQ
CpCQ= 11
= 1:1
20. When the r.m.s value of a source of electricity supply is given as 240v, it means that the peak value of the supply is
Ans: B
Solution
The relationship between the peak value and r.m.s value of electricity supply is given as
Vr.m.s = Vo2
where Vo = peak voltage
∴ Vo = Vr.m.s × √2
= 240 × √2
= 339.5v
= 340v
21. Which of the following operations can be used to convert an alternative current dynamo into a direct current dynamo
Ans: C
Solution
A d.c generator is one in which its current is allowed to flow in one direction even through it may vary in value an a.c generator can only be made to produce a d.c by replacing the two slip rings with a single split ring or commutator.
22.
The net capacitance in the circuit above is
Ans: D
Solution
For capacitance i n parallel, 2µF and 2µF are in parallel,
their equivalence is 2µF and 2µF = 4µF
The 4µF generated is now in series with the remaining 4µF.
The net capacitance for series connection is
1C = 14 + 14 = 1 + 14 = 24
C = 42
= 2µF
23. The instrument used to measure the pressure of a gas is
Ans: D
Solution
Barometer is used to measure atmosphere pressure
Thermometer is used to measure temperature
Hygrometer is used to measure relative density of a liquid
Manometer is used to measure the pressure of a gas
24. 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
Ans: D
Solution
Power is the time rate of doing work
i.e power = energytime
Since energy = mgH
∴ power = mgHt
= 50×10×5t
= 500W
25. A radio station broadcast at a frequency of 600KHZ. If the speed of light in air is 3 × 108ms−1. Calculate the wavelength of the radio wave
Ans: B
Solution
V = fλ
λ = vf
= 3×108600×103 = 500m
= 5 × 102m
N.B 600KHz Frequency = 600 × 103Hz
26. Which of the following is a scalar quantity?
Ans: D
Solution
Scalar quantity is a quantity with only magnitude, it has no direction
Tension, weight, impulse are vector quantities because they have direction. Mass is the only scalar quantity there
27. Determine the focal length of a thin converging lens if the power is 5.0 dioptres
A
B
C
D
Ans: B
Solution
Power of a lens = 1f
f = focal length
f = 1p
= 15
= 0.2m
28. 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]
Ans: D
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 = 80.04
= 200Nm
Since K is constant
For the second case, F = ke
F = 200 × e
∴ e = F200
= 16200
= 0.08m
29. How can energy loss be minimized through Eddy-current?
A
B
C
D
Ans: A
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
30.
A
B
C
D
Ans: B
Solution
c = 8µF, v = 10v
Energy stored = 12 cv2
= 12 × (8 × 10− 6) × 102
= 4 × 10-4
31. A constant force of %n acts for a % seconds on a mass of 5kg initially at rest. Calculate the final momentum
Ans: B
Solution
Impulse = momentum
Impulse = Force (f) × time (t)
Momentum = mass (m) × velocity (v)
∴ Ft = Final momentum – initial momentum
FT = mv – mu
Since it is initially at rest u = 0
∴ 5 × 5 = mv − m(0)
25 = mv
∴ Final momentum = 25kgms−1
32. I. Refraction II. Interference III. Diffraction Which of the above properties are common to all waves?
Ans: B
Solution
Refraction, Interference and diffraction are all properties of waves
33. I. Refraction II. Interference III. Diffraction Which of the above properties are common to all waves?
Ans: B
Solution
Refraction, Interference and diffraction are all properties of waves
34. Which of the following is correct about an electric cell?
Ans: D
Solution
About electric cell
Primary cells are used up gradually often the cells are use and it can’t be recharged
Secondary cells or accumulated can be recharged and used for a long period of time and their main advantage is that they have low internal resistance
35. Which of the following is a semiconductor
Ans: B
Solution
Semi-conductor have an elecctric conductivity intermediate in value between that of a pure metal and a good insulator. Silicon is an example
36. Which of the following surfaces will absorbs radiant heat energy heat?
Ans: C
Solution
A black solution is a better radiator of heat and allow a better absorber of heat.
37. It is known that a neutron exists in a light atomic nucleus
Which of the following also exists in the nucleus?
Ans: D
Solution
Nucleus of atom is made up of neutron and proton
38. The instrument to measure the relative density of light is
Ans: B
Solution
Thermometer is used to measure temperature
Hydrometer is used to measure relative density of liquid.
Spring balance is used to measure the weight of an object
Beaker is used to measure or take volume of a liquid
39. What is the speed of a body vibrating at 50 cyclic per second
Ans: A
Solution
1 cycle = 3600 = 2π rad
∴ 50 cycle = 2 π rad × 50 = 100 πrad
∴ = angular speed = 50 cycles per seconds = 100 π rads−1
40. The action of blotting paper on ink is due to
Ans: C
Solution
Capillarity is the tendency of a liquid to rise or fall in a narrow tube and it explains why a blotting paper absorbs ink
41. When two mirrors are placed at an angle of 900 to each other, how many images will be formed when an object is placed in front of the mirrors
Ans: C
Solution
When two mirror are inclined at an angle θ, the number of images formed, n = 360θ − 1
∴ since θ = 90o
∴ 360θ − 1
= 4 − 1
= 3
42. If silicon is doped with phosphorus, what type of semiconductor material will be formed?
Ans: C
Solution
When silicon is doped with a trivalent atom. A p-type semi-conductor will be formed when silicon is doped with a pentavalent atom such as arsenic, a n-type semi-conductor will be formed
Phosphorous is a pentavalent element, so it will produce a o -type semi-conductor
43. Calculate the angle of minimum deviation of a 60o prism of a refractive index [sin-10.75 = 49o]
Ans: A
Solution
For a refractive index () = sin12(A+D)sin12A
D = angle of minimum deviation
A = refractive angle of the prism
1.5 = sin12(60+D)sin12×60
1.5 = sin12(60+D)sin30
Sin 12 (60 + D) = 1.5 * Sin 30
Sin 12 (60 + D) = 0.75
12 (60 + D) = Sin-1 (0.75)
but Sin-1 (0.75) = 49o
12 (60 + D) = 49
60 + D = 2 * 49 = 98o
D = 98o – 60o
D = 38o
44. What is the cost of running seven 40 W lamps and five 80 W la mps for 12 hours of the electrical energy cost N7.00kWk?
Ans: D
Solution
Seven 40W lamps = 7 × 40 = 280W
Five 80W lamps = 5 × 80 = 400W
Total power = 280W + 400W
= 680W
= 680KW1000 = 0.68KW
The kilowatt hour = 0.68 KW × 12 hrs
= 8.16 KWh
Cost is N 7 per KWh
So the cost of running them = 8.16KWh × N 7/KWh
= 57.12
45.
Ans: B
Solution
V = IR from ohms law
I = VR
Since the resistance are in parallel
1Reff = 18 + 112 + 16
= 2+3+636 = 1136
Reff = 3611 = 3.27
I = I1 + I2 + I3
= VReff= 123.27
= 3.669A
I = 3.7A
46. Calculate the time taken for a mango fruit that fall from the tree 20 m to the ground [g = 10 ms-2]
Ans: D
Solution
u = , H = 20, g = 10
From equation of motion under gravity
H = ut ± 12gt2, It is falling so g is +ve
H = 0 + 12gt2
H = 12gt2
2H = gt2
2Hg = t2
t = 2Hg
= 2×2010
= √4
= 2s
47. Which of the following is not a mechanical wave?
Ans: B
Solution
Mechanical waves require material medium for their propagation only radio waves among the options docs require a material medium
48. The velocity ratio of an inclined plane where angle of inclination in θ is
Ans: D
Solution
Consider an inclined plane shown below, as the effort moves along OB, the load moves is lifted up through a vertical height AB
V.R = distance moved by effortdistance moved by load = OBAB
But Sinθ = opphyp = ABOB
therefore; = OBAB = 1sinθ
49. The volume of a fixed mass of gas is 10cm3 when its pressure is 400cmHg. Determine the volume of the gas when its pressure is 200cmHg.
A
B
C
D
Ans: D
Solution
Using boyle’s law
P1V1 = P2V2
V2 = P1V1200 = 400×10200
= 20cm3
50. Which of the following representations is correct for an atom X with 28 electrons and 30 neutrons?
Correct Option: A
Solution
An atom can be represented thus,
AZX where Z = mass number
A = atomic number
A = number of proton = number of electrons in a free state = 28
Z = number of protons + number of neutrons = 28 + 30 = 58
2858Xis the representation
