## Study Questions

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##### Physics (2017) QUIZ STUDY
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.

1.

Which is the incorrect formula for a body accelerating uniformly?

.
A.

a = v2 - u$$\frac{2}{2}$$

B.

v2 = u2 + 2as

C.

s = $$\frac{1}{2}$$ut + at2

D.

v2 - u2= 2as

Explanation.

s = $$\frac{1}{2}$$ut + at2 is a wrong equation, it should be s = $$\frac{1}{2}$$ut + at2

2.
Which of the following is not an electromagnetic radiation?
.
A. x - ray
C. sunlight
D. sound waves
Explanation.
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.
.
A. 18.57NC$$^{-1}$$
B. 53.06N C$$^{-1}$$
C. 2.28NC$$^{-1}$$
D. 0.80NC$$^{-1}$$
Explanation.
Electric Field Intensity (E) = $$\frac{v}{d}$$

= $$\frac{\text{potential difference}}{\text{distance}}$$

= $$\frac{6.5v}{35cm}$$

= $$\frac{6.5}{35 \times 10^{- 2}}$$

= 18.57NC$$^{-1}$$

4.
Why do soldiers march disorderly while crossing a bridge?
.
A. To prevent resonance on the bridge
B. To set the bridge into resonance
C. To make the b ridge collapse
D. To spread their weight evenly on the bridge
Explanation.
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]

.
A.

0.8N

B.

2.5N

C.

0.5N

D.

1.0N

Explanation.

Upthrust = change in weight

density = $$\frac{\text{mass}}{\text{volume}}$$

Mass of liquid displaced = Density of Liquid $$\times$$ Volume;

= 103 $$\times$$ 50 $$\times$$ 10-6m3

= 0.05kg

(Note that the volume of 50cm3 was converted to m3 by multiplying by 106) i.e 50cm3 = 50 $$\times$$ 10?6m3)

Since mass displaced = 0.05kg

Upthrust = mg = 0.05 $$\times$$ 10

= 0.5N

6.
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
Explanation.
Cathode rays are produced in a discharge tube under Low pressure and high voltage

7.
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
Explanation.
For work to be done, distance must be involved because
workdone = force $$\times$$ distance

8.

Calculate the specific latent heat of vaporization of steam of 1.13 x 106J, if heat energy is required to convert 15kg of it to water.

.
A.

7.53 x 105 Jkg$$^{-1}$$

B.

7.53 x 10-2Jkg$$^{-1}$$

C.

7.53 x 104Jkg$$^{-1}$$

D.

7.53 x 10-3Jkg$$^{-1}$$

Explanation.

Latent Energy = mass(m) $$\times$$ specific latent heat (L)
E = mL

L = $$\frac{E}{m}$$

= $$\frac{1.13 \times 10 ^{6}}{15}$$

= 7.53 $$\times$$ 104Jkg$$^{-1}$$

9.

A cell of internal resistance 2 Ω supplies current to a 6 Ω resistor. The efficiency of the cell is

.
A.

12.00%

B.

25.00%

C.

33.30%

D.

75.00%

Explanation.

Internal resistance determine the maximum current that can be supplied

Efficiency = $$\frac{r}{R}$$ $$\times$$ 100

= $$\frac{2}{6}$$ $$\times$$ 100

= 33.3%

10.
Which of the following statements is NOT correct?
.
A. Molecules of a liquid are stationary
B. Brownian motion is an evidence of particle nature of matter
C. Matter is made up of molecules
D. The molecules of matter are in constant motion
Explanation.
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
.
A. 80.00%
B. 76.60%
C. 66.70%
D. 60.70%
Explanation.
Efficiency = $$\frac{ma}{V.R}$$ x $$\frac{100}{1}$$

V.R = number of pulleys = 6

ma = $$\frac{\text{Load}}{\text{Effort}}$$ = $$\frac{200}{50}$$ = 4

Effiecieny = $$\frac{4}{6}$$ $$\times$$ 100 = 66.67%

12.

Three 3Ω resistance are connected in parallel what is the equivalent resistance?

.
A.

1Ω

B.

9Ω

C.

3Ω

D.

0.33Ω

Explanation.

Resistor connected in a parallel have an equivalence given by
$$\frac{1}{\text{Reff}}$$ = $$\frac{1}{3}$$ + $$\frac{1}{3}$$ + $$\frac{1}{3}$$

= $$\frac{1 + 1 + 1}{3}$$ = $$\frac{3}{3}$$ = 1

Reff = 1Ω

13.
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
Explanation.
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
.
A. protons
B. electrons
C. ions
D. neutrons
Explanation.
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
.
A. Balance wheel of a watch
B. Construction of steel rail lines
C. Construction of large steel bridges
D. Fitting of tyres on wheels
Explanation.
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
.
A. kgm
B. µm
C. Jm
D. µm$$^{-1}$$
Explanation.
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

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
.
A. 80.00%
B. 76.60%
C. 66.70%
D. 60.70%

18.

Calculate the light of the image formed by a pinhole camera of length 12cm used to photograph an object 60cm away from the hole and 70cm high

.
A.

10 cm

B.

16 cm

C.

5 cm

D.

14 cm

Explanation.

Magnification = $$\frac{\text{Length of camera}}{\text{distance of object from pin hole}}$$

m = $$\frac{12}{60}$$

= 0.2

Also magnification m = $$\frac{\text{Height of image}}{\text{Height of object}}$$

ΔHeight of image = m $$\times$$ height of object

= 0.2 $$\times$$ 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

.
A.

1:04

B.

4:01

C.

1:01

D.

2:01

Explanation.

H = mcΔ

HP = HQ, ΔP = 2Δq,

mP = $$\frac{1}{2}$$mQ

Δ HP = mQCPΔP, also HQ = mQCQΔQ

Since HP = HQ

mPcPΔP = mQcPΔq

Putting in the conditions

$$\frac{1}{2}$$mQ $$\times$$ cP $$\times$$ 2ΔQ = mQ $$\times$$ ΔQ $$\times$$ cQ

cP = cQ

$$\frac{C_p}{C_Q}$$= $$\frac{1}{1}$$

= 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

.
A.

240v

B.

340v

C.

480v

D.

57600v

Explanation.

The relationship between the peak value and r.m.s value of electricity supply is given as

V$$_{r.m.s}$$ = $$\frac{V_o}{\sqrt{2}}$$

where Vo = peak voltage

Vo = V$$_{r.m.s}$$ x $$\sqrt{2}$$

= 240 x $$\sqrt{2}$$

= 339.5v

= 340v

21.
Which of the following operations can be used to convert an alternative current dynamo into a direct current dynamo
.
A. number of turns in the coil is increased
B. strength of the field magnet is increased
C. slip rings are replaced with split ring cummutator
D. coil is wound on a soft iron armature
Explanation.
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

.
A.

80µF

B.

6.0µF

C.

4.0µF

D.

2.0µF

Explanation.
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

$$\frac{1}{C}$$ = $$\frac{1}{4}$$ + $$\frac{1}{4}$$ = 1 + $$\frac{1}{4}$$ = $$\frac{2}{4}$$

C = $$\frac{4}{2}$$

= 2µF

23.
The instrument used to measure the pressure of a gas is
.
A. barometer
B. thermometer
C. hygrometer
D. manometer
Explanation.
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

.
A.

100w

B.

200w

C.

400w

D.

500w

Explanation.

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

25.

A radio station broadcast at a frequency of 600KHZ. If the speed of light in air is 3 $$\times$$ 108ms$$^{-1}$$. Calculate the wavelength of the radio wave

.
A.

2.20 $$\times$$ 10$$^3$$m

B.

5.0 $$\times$$ 10$$^2$$m

C.

5.0 $$\times$$ 10$$^5$$m

D.

11.8 $$\times$$ 10$$^{11}$$m

Explanation.

V = fλ

λ = $$\frac{v}{f}$$

= $$\frac{3 \times 10^8}{600 \times 10^3}$$ = 500m

= 5 $$\times$$ 102m

N.B 600KHz Frequency = 600 $$\times$$ 103Hz

26.
Which of the following is a scalar quantity?
.
A. Tension
B. Weight
C. Impulse
D. Mass
Explanation.
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. 0.1 m
B. 0.2 m
C. 2.0 m
D. 2.5 m
Explanation.
Power of a lens = $$\frac{1}{f}$$

f = focal length

f = $$\frac{1}{p}$$

= $$\frac{1}{5}$$

= 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$$^{-2}$$]

.
A.

0.04m

B.

0.12m

C.

0.01m

D.

0.08m

Explanation.

From Hoke's Law, F = ke, K = Constant of Force

For he first case, Force = mg,

= 0.8 $$\times$$ 10 = 8N

8 = k $$\times$$ 0.04

k = $$\frac{8}{0.04}$$

= $$\frac{200N}{m}$$

Since K is constant

For the second case, F = ke

F = 200 $$\times$$ e

e = $$\frac{F}{200}$$

= $$\frac{16}{200}$$

= 0.08m

29.
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
Explanation.
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.

From the diagram above, calculate the energy stored in the capacitor

.
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

Explanation.

c = 8µF, v = 10v

Energy stored = $$\frac{1}{2}$$ cv2

= $$\frac{1}{2}$$ $$\times$$ (8 $$\times$$ 10-6) $$\times$$ 102

= 4 $$\times$$ 10$$^{-4}$$

31.

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

Explanation.

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 x 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?
.
A. II and III only
B. I, II and III
C. I and II only
D. I and III only
Explanation.
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?
.
A. II and III only
B. I, II and III
C. I and II only
D. I and III only
Explanation.
Refraction, Interference and diffraction are all properties of waves

34.
Which of the following is correct about an electric cell?
.
A. Primary cell produces a large current for a long time
B. Secondary cell has a very high internal resistance
C. Primary cell has a very low internal resistance
D. Secondary cell has a very low internal resistance
Explanation.
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
.
A. copper
B. silicon
C. plastic
D. Iron
Explanation.
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?
.
A. white
B. red
C. black
D. blue
Explanation.
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?

.
A.

An electron

B.

α - particle

C.

β - particle

D.

proton

Explanation.

Nucleus of atom is made up of neutron and proton

38.
The instrument to measure the relative density of light is
.
A. thermometer
B. hydrometer
C. spring balance
D. beaker
Explanation.
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

.
A.

100 rads$$^{-1}$$

B.

200 rads$$^{-1}$$

C.

50 rads$$^{-1}$$

D.

400 rads$$^{-1}$$

Explanation.

1 cycle = 3600 = 2 rad

angular speed = 50 cycles per seconds = 100 rads$$^{-1}$$

40.
The action of blotting paper on ink is due to
.
A. diffusion
B. osmosis
C. capillarity
D. surface tension
Explanation.
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 90º to each other, how many images will be formed when an object is placed in front of the mirrors

.
A.

5

B.

4

C.

3

D.

2

Explanation.

When two mirror are inclined at an angle $$\theta$$, the number of images formed, n = $$\frac{360}{\theta}$$ - 1

since $$\theta$$ = 90o

$$\frac{360}{\theta}$$ - 1

= 4 - 1

= 3

42.
If silicon is doped with phosphorus, what type of semiconductor material will be formed?
.
A. Zener material
B. P-n junction
C. n-type
D. p-type
Explanation.
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]
.
A. 38.00o
B. 19.47o
C. 16.25o
D. 49o
Explanation.
For a refractive index () = $$\frac{\sin\frac{1}{2} (A + D)}{\sin\frac{1}{2}A}$$

D = angle of minimum deviation

A = refractive angle of the prism

1.5 = $$\frac{\sin\frac{1}{2} (60 + D)}{\sin\frac{1}{2} \times 60}$$

1.5 = $$\frac{\sin\frac{1}{2} (60 + D)}{\sin 30}$$

Sin $$\frac{1}{2}$$ (60 + D) = 1.5 * Sin 30

Sin $$\frac{1}{2}$$ (60 + D) = 0.75

$$\frac{1}{2}$$ (60 + D) = Sin-1 (0.75)

but Sin-1 (0.75) = 49o

$$\frac{1}{2}$$ (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?
.
A. N80.00
B. N45.36
C. N65.00
D. N57.12
Explanation.
Seven 40W lamps = 7 $$\times$$ 40 = 280W

Five 80W lamps = 5 $$\times$$ 80 = 400W

Total power = 280W + 400W

= 680W

= $$\frac{680KW}{1000}$$ = 0.68KW

The kilowatt hour = 0.68 KW $$\times$$ 12 hrs

= 8.16 KWh

Cost is N 7 per KWh

So the cost of running them = 8.16KWh $$\times$$ N 7/KWh

= 57.12

45.

From the diagram above, calculate the total current in the circuit

.
A.

5.0A

B.

3.7A

C.

4.5A

D.

4.0A

Explanation.
V = IR from ohms law

I = $$\frac{V}{R}$$

Since the resistance are in parallel

$$\frac{1}{Reff}$$ = $$\frac{1}{8}$$ + $$\frac{1}{12}$$ + $$\frac{1}{6}$$

= $$\frac{2 + 3 + 6}{36}$$ = $$\frac{11}{36}$$

Reff = $$\frac{36}{11}$$ = 3.27

I = I1 + I2 + I3

= $$\frac{V}{Reff}$$= $$\frac{12}{3.27}$$

= 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]

.
A.

10s

B.

5s

C.

4s

D.

2s

Explanation.
u = ?, H = 20, g = 10

From equation of motion under gravity

H = ut ± $$\frac{1}{2}$$gt2, It is falling so g is +ve

H = 0 + $$\frac{1}{2}$$gt2

H = $$\frac{1}{2}$$gt2

2H = gt2

$$\frac{2H}{g}$$ = t2

t = $$\frac{\sqrt{2H}}{g}$$

= $$\frac{\sqrt {2 \times 20}}{10}$$

= $$\sqrt{4}$$

= 2s

47.
Which of the following is not a mechanical wave?
.
A. wave in closed pipe
C. water waves
D. sound waves
Explanation.
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 ? is
.
A. Sin?
B. Cos?
C. Tan?
D. $$\frac{1}{\sin \theta}$$
Explanation.
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 = $$\frac{\text{distance moved by effort}}{\text{distance moved by load}}$$ = $$\frac{OB}{AB}$$

But Sin? = $$\frac{opp}{hyp}$$ = $$\frac{AB}{OB}$$

therefore; = $$\frac{OB}{AB}$$ = $$\frac{1}{\sin \theta}$$

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. 30cm3
B. 40cm3
C. 50cm3
D. 20cm3
Explanation.
Using boyle's law

P1V1 = P2V2

V2 = $$\frac{P_1 V_1}{200}$$ = $$\frac{400 \times 10}{200}$$

= 20cm3

50.
Which of the following representations is correct for an atom X with 28 electrons and 30 neutrons?
.
A. $$^{58}_{28}X$$
B. $$^{30}_{28}X$$
C. $$^{28}_{30}X$$
D. $$^{58}_{30}X$$
Explanation.
An atom can be represented thus,

$$^{Z}_{A}X$$ 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

$$^{58}_{28}X$$is the representation