Physics 2018 JAMB Past Questions

1. A man walks 1km due east and then 1 km due north His displacement

A. √2km N 45°E
B. 1km N 30°E
C. 1km N 15°E
D. √2km N 60°E

Correct Answer: Option A

2. The density of 400cm of palm oil was 0.9gcm-3 before frying. If the density of the oil was 0.6gm-3 after frying, assuming no loss of oil due to spilling, its new volume was?

A. 1360cm $^{3}$

B. 600cm

^{3}

C. 240cm

^{3}

D. 8000m

^{3}

Correct Answer: Option B

Explanation

D e n s i t y = \frac{m a s s}{v o l u m e}

⇒

0.9 g c m^{- 3} = \frac{m a s s}{400 c m^{3}} = 360 g

without any loss in the frying process, we have

0.6 g c m^{- 3} = \frac{360 g}{v}

v = \frac{360 g}{0.6 g c m^{- 3}} = 600 c m^{3}

3. Natural radioactivity consists of the emission of

A. α- particles and β-rays
B. α- particles and X-rays
C. α- particles, β - rays and g-rays
D. γ- rays and X-rays

Correct Answer: Option C

4.Which of the following is true of an electrical charge?

A. Positive charge means deficit electrons
B. Negative charge means excess of electrons
C. electric current means movement of electrons
D. All of the above

Correct Answer: Option D

5. Which of the following does NOT describe the Image formed by a plane minor?

A. Erect
B. Laterally inverted
C. Same distance from mirror as object
D. Magnified

Correct Answer: Option D

Explanation

The image formed by a plane mirror is always virtual (the light rays do not actually come from the image), upright, and of the same shape and size as the object it is reflecting.

What is the resultant resistance of the circuit in the image shown?

A. 8Ω
B. 11Ω
C. 4Ω
D. 3.6Ω

Correct Answer: Option A

7. Which of the following best describes the energy changes which take place when a steam engine drives a generator which lights a lamp?

A. heat ----> Light----> Sound ----> Kinetic
B. Kinetic ----> Light ----> Heat ----> Electricity
C. heat ----> Kinetic ----> Electricity ----> Heat and Light
D. electricity ----> Kinetic ----> Heat ----> Light

Correct Answer: Option C

8. Cathode rays are

A. High-energy electromagnetic waves
B. protons
C. neutrons
D. streams of electrons

Correct Answer: Option D

9. A narrow beam of white light can be split up into different Colours by a glass prism. The correct explanation is that

A. white light Is an electromagnetic wave
B. the prism has all the colours of the white light
C. different colours of white light travel with different speeds in glass
D. white light has undergone total Internal reflection in the prism

Correct Answer: Option C

The diagram shown represents a block-and-tackle pulley system on which an effort of W Newtons supports a load of 120.0N. If the efficiency of the machine is 40, then the value of W is?

A. 28.0
B. 48.0N
C. 233.0N
D. 50.0N

Correct Answer: Option D

11. What type of reaction is represented by the following scheme?

_{1}^{2} X

_{1}^{2} Y

----->

_{2}^{3} Z

_{1}^{0} n

+ energy

A. fusion reaction
B. fission reaction
C. Chain reaction
D. radioactive decay

Correct Answer: Option A

12. The amount of heat needed to raise the temperature of 10kg of Copper by 1K is its

A. specific heat capacity
B. latent heat
C. heat capacity
D. internal energy

Correct Answer: Option C

13. The electrochemical equivalent of silver is 0.0012g/C. If 36.0g of silver is to be deposited by electrolysis on a surface by passing a steady current for 5mins, the current must be?

A. 6000A
B. 100A
C. 10A
D. 1A

Correct Answer: Option B

14. Shadows and eclipses result from the

A. refraction of light
B. reflection of light
C. defraction of light
D. rectilinear propagation of light

Correct Answer: Option D

15.Which of the following obeys Ohm's law?

A. all metals
B. diode only
C. all electrolytes
D. glass

Correct Answer: Option A

16. Which of the following statements are TRUE of isotopes?

I. Isotopes of an element have the same chemical properties because they have the same number of electrons
II. Isotopes of elements are normally separated using physical properties
III. Isotopes of an element have the same number of protons in their nuclei

A. I and II only
B. I and III only
C. II and III only
D. I, II and III

In the diagram given the hanging mass m2 is adjusted until m1 is on the verge of sliding. The coefficient of static

A. $\frac{m_{1}}{m_{2}}$

\frac{m_{1} g}{m_{2}}

\frac{m_{2}}{m_{1}}

\frac{m_{2} g}{m_{1}}

Correct Answer: Option D

18. Which of the following may be used to explain a mirage?

I. Layers of air near the road surface have varying refractive indices in hot weather
II. Road surfaces sometimes become good reflectors in hot weather
III. Light from the sky can be reflected upwards after coming close to the road surface.

A. I and III only
B. II and III only
C. II only
D. I, II and III

Correct Answer: Option A

In the diagram given if the atmospheric pressure is 760mm, the pressure in the chamber G Is

A. 660mm
B. 890mm
C. 690mm
D. 860mm

Correct Answer: Option B

20. Which of the following has the lowest internal resistance when new?

A. Leclanche cell
B. Daniell cell
C. Torch battery
D. Accumulator

Correct Answer: Option D

21.The pitch of an acoustic device can be increased by

A. decreasing the loudness
B. increasing the intensity
C. increasing the frequency
D. decreasing the intensity

Correct Answer: Option C

22. One of the features of the fission process is that

A. it leads to chain reaction
B. its products are not radioactive
C. neutrons are not released
D. the of the masses of the reactants equals the sum of the masses of the products

Correct Answer: Option A

23. The linear expansivity of brass is 2 x 10

. If the volume of a piece of brass is 15.00cm at 0°C, what is the volume at 100°C

A. 16.03cm
B. 15.09cm
C. 16.00cm
D. 15.03cm

Correct Answer: Option B

Explanation

Volume Expansivity

γ

3 α

γ = 3 \times 2 \times 10^{- 5}

γ = 6 \times 10^{- 5} C^{- 1}

V_{2} = V_{1} (1 + γ θ)

V_{2} = 15 (1 + (6 \times 10^{- 5} \times (100 - 0)))

V_{2} = 15 (1.006)

15.09 c m^{3}

24.A lead bullet of mass 0.05 kg is fired with a velocity of 200 ms into a lead block of mass 0.95 kg. Given that the lead block can move freely. the final kinetic energy after impact is

A. 100J
A. 150J
C. 50J
D. 200J

Correct Answer: Option C

25. In a series R-L-C circuit at resonance, the voltages across the resistor and the inductor are 30V and 40V respectively. What is the voltage across the capacitor?

A. 30V
B. 70V
C. 50V
D. 40V

Correct Answer: Option D

26. If the fraction of the atoms of a radioactive material left after 120years is

\frac{1}{64}

, what is the half-life of the material?

\frac{1}{64}

A. 20 years
B. 10 years
C. 2 years
D. 24 years

Correct Answer: Option A

In the diagram shown, which of the simple pendulum will resonate with P when set into oscillation?

A. U
B. T
C. R and T
D. Q and R

Correct Answer: Option B

28.The time rate of loss of heat by a body is proportional to the

A. temperature of its surroundings
B. temperature of the body
C. difference in temperature between the body and its surroundings
D. ratio of the temperature of the body to that of its surroundings

Correct Answer: Option C

29.A positively charged rod X is brought near an uncharged metal sphere Y and is then touched by a finger with X still in place. When the finger is removed, the result is that Y has

A. no charge and a zero potential
B. a positive charge and a zero potential
C. a negative charge and a positive potential
D. a negative charge and a negative potential

Correct Answer: Option D

30. Electrical appliances in homes are normally earthed so that

A. a person touching the appliances is safe from electric shock
B. both the a.c. and d.c. sources can be used
C. the appliances are maintained at a higher pd than the earth
D. the appliances are maintained at a lower pd than the earth

Correct Answer: Option D

31. Gamma rays are produced when

A. high velocity electrons are abruptly stopped in metals
B. energy changes occur within the nucleus of atoms
C. energy changes occur within the electronic structure of atoms
D. electrons are deflected in very strong magnetic fields

Correct Answer: Option B

32.What is the speed of a particle of mass 10^-27kg whose wavelength is 10^-8m.

[h = 6.63 x 10^-34Js]

A. 6.63ms^-1
B. 66.30ms^-1
C. 663.00ms^-1
D. 6630.00ms^-1

Correct Answer: Option B

Explanation

Energy of a particle is given by
E = hf = hV/λ (since V = fxλ)
But in terms of mass M, E = ∆MV²
∴ ∆MV² = hV/λ
∆MV = h/λ
∴ V = h/λ∆M
V = 6.63 x 10^-34/(10^-27 x 10^-8)
V = 6.63 x 10^-34/10^-35
V = 6.63 x 10^-34+35
V = 6.63 x 10
V = 66.3ms^-1

33.in a series R-L-C circuit at resonance, the voltages across the resistor and the inductor are 30V and 40V respectively, what is the voltage across the capacitor?

A. 30V
B. 40V
C. 50V
D. 70V

Correct Answer: Option B

Explanation

At resonance, inductive reactant X_L is equal to the capacitive reactance X_C
i.e. X_L = X_C
and X_L = V_L/I_L
and X_C = V_C/I_C

Again since the components are in series, the same current flows in the series arrangment
i.e. I_L = I_C
at resonance, V_L/I_L = V_C/I_C
∴ V_L = V_C
= 40V

34.In the Rutherford scattering experiment, a beam of alpha particles was fired at a thin gold film with some of the particles being considerably deflected. This shows that

A. a gold nucleus contains protons, neutrons and electrons uniformly distributed in a tiny volume
B. the gold nucleus is positively charged and is concentrated in a tiny volume
C. the gold nucleus emitted alpha particles
D. the gold nucleus is concentrated in a tiny volume and contains alpha particles

Correct Answer: Option B

35²³₁₁Na + Proton → ^p_qX + alpha particle
What are the values of p and q respectively in the equation above?

A. 10 and 20
B. 12 and 24
C. 20 and 10
D. 24 and 12

Correct Answer: Option C

Explanation

²³₁₁Na + Proton → ^p_qX + alpha particle
Represent;
²³₁₁Na + ¹₁P → ^p_qX + ⁴₂He

Thus from the above equations, p = 20 and q = 10

36. A semiconductor diode is used in rectifying alternating current into direct current mainly because it

A. allows current to flow in either direction
B. is non-linear
C. offers a high input resistance
D. allows current to flow only in one direction

Correct Answer: Option D

Explanation

A rectifier of an alternating current is a device which allows the flow of current only in one direction

37.if ∆x is the uncertainty in the measurement of the position of a particle along the x-axis and ∆P_x is the uncertainty in the measurement of the linear momentum along the x-axis, then the uncertainty principle relation is given as

A. ∆x ∆P_x ≥ h
B. ∆x ∆P_x = 0
C. ∆x ∆P_x < h
D. ∆x ∆P_x = ∞

Correct Answer: Option A

38.When a ship sails from salt water into fresh water, the fraction of its volume above the water surface will

A. increase
B. decrease
C. remain the same
D. increase then decrease

Correct Answer: Option B

Explanation

Fresh water is less dense than the salt water, hence when the ship sails in fresh water, it will sink more, thus the fraction of the ship above the water surface will decrease.

I. Its velocity is constant
II. No work is done on the body
III. It has constant acceleration directed away from the centre
IV. The centripetal force is directed towards the centre

Which combination of the above is true of a body moving with constant speed in a circular track?

A. II and IV
B. I and IV
C. II and III
D. I and III

Correct Answer: Option A

40.The velocity ratio of a machine is 5 and its efficiency is 75%. What effort would be needed to lift a load of 150N with the machine?

A. 20N
B. 30N
C. 40N
D. 50N

Correct Answer: Option C

Explanation

Efficiency = M.A/V.R
75% = M.A/V.R
75/100 = M.A/5
M.A = 75(5)/100 = 3.75

But M.A = Load/Effort
3.75 = 150/Effort
Effort = 150/3.75
Effort = 40N

41. The energy needed to move a unit positive charge around a complete electric circuit is called the

A. electromotive force
B. electric potential difference
C. electric energy
D. kinetic energy

Correct Answer: Option B

Explanation

Electric potential difference: work needed per unit of charge to move a test charge between the two points.
Electric energy: energy derived from electric potential energy.
Kinetic energy: moving energy

42. The inner diameter of a small test tube can be measured accurately using a

A. Micrometres screw gauge
B. Pair of dividers
C. Metre rule
D. Pair of vernier calliper

Correct Answer: Option D

Explanation

A vernier scale is a visual aid to take an accurate measurement reading between two graduation markings on a linear scale by using mechanical interpolation; thereby increasing resolution and reducing measurement

43.A pulley system has three pulleys in the fixed block and two in the movable block and if the pulley has an efficiency of 72%, the mechanical advantage of the system is?

A. 36.0
B. 7.2
C. 5.0
D. 3.6

Correct Answer: Option D

Explanation

Mechanical Advantage = V.R × Efficiency
= 5 × 0.72
= 3.6

44.When an atom loses or gain a charge it becomes

A. An electron
B. An ion
C. A neutron
D. A proton

Correct Answer: Option B

Explanation

If an atom gains or loses an electron, it becomes an ion. An atom that gains a negative electron, it becomes a negative ion. If it loses an electron it becomes a positive ion

45.A ball of mass 800g moving horizontally with a speed of 5m/s hits a vertical wall and rebounds with the same speed. The impulse experienced by the ball is?

A. 0kgm
B. 2kgm/s
C. 4kgm/s
D. 8kgm/s

Correct Answer: Option D

Explanation

Initial momentum = (0.8) × (5)
= 4.0kgms

^{- 1}

Final momentum
= (0.8) × (– 5)
= – 4.0kgms

^{- 1}

Impulse on ball
= Change in momentum
= 4.0 – (– 4.0)
= 8.0.0kgms

^{- 1}

46.The force between the molecules of a liquid in contact with that of a solid is?

A. Adhesive
B. Cohesive
C. Magnetic
D. Repulsive

Correct Answer: Option B

Explanation

Cohesion is the inter-molecular attractive force acting between two adjacent portions of a substance, particularly of a solid or liquid. It is this force that holds a piece of matter together

47.A body of mass 100g moving with a velocity if 10ms-1 collides with a wall. If after collision it moves with a velocity of 2.0ms−1 in the opposite direction, calculate the change in momentum.

A. 0.8Ns
B. 1.2Ns
C. 12.0Ns
D. 80.0Ns

Correct Answer: Option A

Explanation

Momentum = Mass x Velocity
Change in Momentum = Mass x (change in velocity)
Change in Momentum = Mass x (v - u)
Mass = 100g = 0.1kg
U = 2ms

V = 10ms

Change in momentum = m (v − u)
= 0.1 (10 − 2)
= 0.1 (8)
= 0.8Ns

48.A 20kg mass is to be pulled up a slope inclined at 30° to the horizontal. If efficiency of the plane is 75%. The force required to pull the load up the plane is J [g=10ms

^{- 2}

]

^{- 2}

A. 87N
B. 73.5N
C. 133.3N
D. 533.2N

Correct Answer: Option C

Explanation
V. R = $\frac{1}{S i n θ}$
m = 20kg
V.R = $\frac{1}{S i n 30}$
= 2
Efficiency = 75%
Load = mg
= 20 x 10 = 200N
Efficiency = $\frac{M . A}{V . R} \times 100$
75/100 = $\frac{M . A}{2}$
M .A = $\frac{75 \times 2}{100}$
M. A = 1.5
Since M. A. = $\frac{Load}{Force}$
Force = $\frac{200}{1.5}$
= 133.3N

49. The tendency of a body to remain at rest when a force is applied to it is called.

A. Impulse
B. Momentum
C. Inertia
D. Friction

Correct Answer: Option C

Explanation

Inertia, property of a body by virtue of which it opposes any agency that attempts to put it in motion or, if it is moving, to change the magnitude or direction of its velocity. Inertia is a passive property and does not enable a body to do anything except oppose such active agents as forces and torques. A moving body keeps moving not because of its inertia but only because of the absence of a force to slow it down, change its course, or speed it up.
There are two numerical measures of the inertia of a body: its mass, which governs its resistance to the action of a force, and its moment of inertia about a specified axis, which measures its resistance to the action of a torque about the same axis.

50. An object is placed 20cm from a concave mirror of focal length 10cm. The linear magnification of the image produced is?

A. 0
B. $\frac{1}{2}$

C. 1
D. 2

Correct Answer: Option C

Explanation

\frac{I}{V}

\frac{1}{f}

–

\frac{1}{u}

\frac{I}{V}

\frac{1}{10}

–

\frac{1}{20}

\frac{1}{20}

V
V = 20cm.
M =

\frac{V}{U}

\frac{20}{20}

= 1

51. The energy needed to move a unit positive charge around a complete electric circuit is called the

A. electromotive force
B. electric potential difference
C. electric energy
D. kinetic energy

Correct Answer: Option B

Explanation

A force of 5N acts at a point Y on a rod XYZ as shown in this diagram. If XYZ is 2m, what is the moment of the force about point X?

A. 0Nm
B. 3Nm
C. 7Nm
D. 10Nm

Correct Answer: Option D

Explanation

Moment = Force × Distance
= 5N x 2m
= 10Nm

53. The resistance of a 40W car head lamp, drawing current from a 12V battery is ____.

A. 0.3Ω
B. 3.3Ω
C. 3.6Ω
D. 4.8Ω

Correct Answer: Option C

Explanation

Power delivered to head lamp =

\frac{V_{2}}{R}

= 40W
R =

\frac{V_{2}}{40}

\frac{(12 \times 2)}{40}

= 3.6Ω

54. A beam of light is incident from air to water at an angle of 300. Find the angle of refraction if the refractive index of water is 4/3

^{o}

B. 18 $^{o}$
C. 22 $^{o}$
D. 24 $^{o}$ $^{o}$ $^{o}$

Correct Answer: Option C

Explanation

X =

\frac{4}{3}

r = ?
Shell’s law:. 7 =

\frac{S i n 2^{0}}{S i n r^{0}}

\frac{V}{g}

\frac{S i n 30^{0}}{S i n r^{0}}

Sin

r^{0}

\frac{3 S i n 30^{0}}{4}

Sin

r^{0}

= 0.375
R

^{o}

= Sin-1 (0.375)
R

^{o}

= 22.02

^{o}

^{o}

= 22

^{o}

55. An electric heating coil rated at 1Kw is used to heat 2kg of water for 2 minutes. The initial water temperature is 30

^{o}

C. Taking the specific heat of the water as 4,000Jkg

^{- 1}

and neglecting that of the container, the final water temperature is

A. 15.0

^{o}

B. 45.0

^{o}

C. 52.5

^{o}

C. 60.0

^{o}

Correct Answer: Option B

Explanation

Power = 1kw=100W
Time = 2mins = 2 × 60 = 120secs
Energy = power × time
1000 × 120 = 120,000J
Energy = mc(θ

_{2}

– θ

_{1}

)

120,000 = 2 × 4000(θ

_{2}

– θ

_{1}

)

_{1}

θ2 = 30 + 15 = 45

^{o}

56.What flows to the earth by connecting the conductor to the earth?

A. Electrons
B. Ion
C. Neutron
D. Proton

Correct Answer: Option A

Explanation

Ion: an atom with a net electric charge due to loss or gain of one or more electrons
Neutron: a subatomic particle of about the same mass as a proton without electric charge.
Proton: a subatomic particle with a positive charge

57. Temperature is the property of a body which is proportional to the ____.

A. total kinetic energy of its molecules
B. average kinetic energy of its molecules
C. average speed of its molecules
D. maximum speed of its molecules

Correct Answer: Option B

Explanation

[Average kinetic energy of its molecules]

58. The product of force and time is?

A. Impulse
B. Momentum
C. Inertia
D. Friction

Correct Answer: Option A

Explanation

An impulse is equal to the net force on the object times the time period over which this force is applied. Impulse is derive from the equation F = ma, which comes from Newton's second law of motion

59. Which of the following concepts is not an evidence of the particles nature of matter?

A. Diffusion
B. Brownian motion
C. Diffraction
D. Crystallization

Correct Answer: Option D

Explanation

Diffusion is the net movement of molecules/atoms from a region of high concentration to low concentration.
Brownian motion is the erratic random movement of microscopic particles in a field.
Diffraction is the various phenomena that occur when a wave encounters an obstacle.

60. A car traveled at a uniform speed of 100km/h, spends 15m moving from point A to point B along its route. The distance between A and B is

A. 50km
B. 25km
C. 15km
D. 10kM61. A solid cube of side 50cm and mass 75kg floats in a liquid with $\frac{1}{3}$

Correct Answer: Option B

Explanation

Distance = speed × time
=

\frac{(\frac{100 \times 103}{3600})}{15 \times 60}

= 25km

61. of its height above the liquid surface. The relative density of the liquid is?

A. 0.33
B. 0.50
C. 0.67
D. 0.90

Correct Answer: Option D

Explanation

Volume of liquid displaced =

\frac{2}{3}

(0.5)

^{3}

Mass of liquid displaced = mass of floating cube = 75kg
Density of liquid =

\frac{m a s s}{v o l u m e}

\frac{75}{(\frac{7}{3 (0.5)})}

× 3
= 0.9 × 103kgm

^{- 3}

R.D of liquid =

\frac{(0.9)}{(1.0)}

× 103 = 0.9

62. A man hears his echo from a nearby hill 2s after he shouted. If the frequency of his voice is 260Hz and the wavelength is 1.29m, how far away is the hill

A. 330.0m
B. 335.4m
C. 660.0m
D. 670.8m

Correct Answer: Option B

Explanation

Recall V = F × lambda
= 260 × 1.29
= 335.4ms

^{- 1}

63. Which of the following is an essential physical property of the wires uses for making fuses ?

A. Low density
B. Hypothermal conductivity
C. Low electrical resistivity
D. Low melting point

Correct Answer: Option D

Explanation

Fuse wires have a low melting point so that if a huge amount of current is passed through it to any appliance than that wire would melt and stop the appliance from getting damaged by not letting the current pass any further.

64. A 40W instrument has a resistance 90 Ohms. On what voltage should it be operated normally

A. 60V
B. 150V
C. 225V
D. 360V

Correct Answer: Option A

Explanation

P = 40W
R = 90W
V = ?
P =

\frac{V^{2}}{R}

^{2}

= PR = 40 x 90
V

^{2}

= 3000
V = √3600
V = 60N

65. Mercury which is spilled onto a glass surface forms ball-like shapes because____.

A. Mercury is a metal
B. The cohesive force between its molecules is greater than the adhesive force between mercury and glass molecules
C. The cohesive force between its molecules is less than the adhesive force between mercury and glass molecules
D. The viscosity of mercury is height

Correct Answer: Option B

Explanation

In case of small drops of mercury, the gravitational potential energy is negligible in comparison to the potential energy due to surface tension.Consequently, to keep the drop in equilibrium, the mercury drop’s surface tends to contract so that its surface area will be the least for a sphere and the drops will be spherical.
But in the case of bigger drops of mercury, the potential energy due to gravity is predominant over the potential energy due to surface tension.Consequently, to keep equilibrium , the mercury drop tends to assume minimum potential energy as possible, the drop becomes oval in shape and lower center of gravity.

66. Water of mass 150g at 60

^{o}

c is added to 300g of water at 20

^{o}

c and the mixture is well stirred. Calculate the temperature of the mixture.(neglect heat losses to the surroundings)

^{o}

A. 33 $^{o}$ c
B. 40 $^{o}$ c
C. 25 $^{o}$ c
D. 10 $^{o}$ c

Correct Answer: Option A

Explanation

Water 1 => M = 150g = 0.15kg,
θ

_{2}

= 60

^{o}

C; θ

_{1}

= θ
Q

_{1}

= MC (θ

_{2}

– θ

_{1}

)

_{1}

= 0.15C (60 - θ)
Water 2 => M = 300g = 0.3kg
θ1 = 20

^{o}

C, θ

_{2}

= θ
Q2 = MC (θ

_{2}

– θ

_{1}

)
= 0.3C (θ – 20)
Combining Q1 and Q2
0.15C (60 - θ) = 0.3C (θ – 20)
9 – 0.15θ = 0.3θ – 6
0.3θ + 0.15θ = 9 + 6
0.45 θ = 15
θ = 33.33

^{o}

67. Which of the following phenomena is the practical evidence for the existence of the continual motion of molecules.

A. Transitional Motion
B. Rotational Motion
C. Brownian Motion
D. Oscillatory Motion

Correct Answer: Option C

Explanation

Brownian motion, also called Brownian movement, any of various physical phenomena in which some quantity is constantly undergoing small, random fluctuations.
If a number of particles subject to Brownian motion are present in a given medium and there is no preferred direction for the random oscillations, then over a period of time the particles will tend to be spread evenly throughout the medium.

68. The process by which protons are converted into helium atoms with a tremendous release of energy is called?

A. thermionic emission
B. nuclear fission
C. thermonuclear fusion
D. photoelectric emission

Correct Answer: Option C

Explanation

Thermionic emission: thermally induced flow of charge
Nuclear fission: nuclear reaction or a radioactive decay process
Photoelectric emission: emission of electrons or other free carriers when light shines on a material

Which of the following is not a product of nuclear fusion?

A. X – ray
B. Y –ray
C. α – particles
D. neutron

Correct Answer: Option A

Explanation

Y – Ray is a penetrating electro-magnetic radiation.
α – particle is produced in the process of alpha decay.
Neutron is a sub-atomic particle.

70. A room is heated by means of a charcoal fire, an occupants of the room standing away from the fire is warmed mainly by

A. Convection
B. Radiation
C. Conduction
D. Reflection

^{o}

^{o}

Correct Answer: Option B

Explanation

Radiation refers to the transmission of energy as electromagnetic radiation from its emission at a heated surface to its absorption on another surface, a process requiring no medium to convey the energy.
Conduction is the transferring of heat by direct contact.
Convection is transferring heat through the motions of fluids (gases and liquids).

^{o}

For what values of F and θ will the forces shown in the diagram below be in equilibrium.

A. 60N and 60 $^{o}$

B. 60N and 30 $^{o}$
C. 20√3 N and 60 $^{o}$
D. 20√3N and 30 $^{o}$

Correct Answer: Option A

Explanation

Resolve vertically, 40cosθ = 20, θ = 60

^{o}

Resolve horizontally, f = 40sinθ = 40sin60

^{o}

= 40(

\frac{\sqrt{3}}{2}

)
= 20√3 N

72. Which of the following phenomena cannot be explained by the molecular theory of matter?

A. Conduction
B. Convection
C. Expansion
D. Radiation

Correct Answer: Option D

Explanation

Conduction: the flow of internal energy from a region of higher temperature to lower temperature
Convection: heat transfer due to bulk movement of molecules within fluids
Expansion: the action of becoming larger or more extensive

73. The friction which exist between two layers of liquid in relative motion is called.

A. Capillary
B. Surface
C. Viscosity
D. Cohesion

Correct Answer: Option C

Explanation

Viscosity, resistance of a fluid (liquid or gas) to a change in shape, or movement of neighboring portions relative to one another. Viscosity denotes opposition to flow. The reciprocal of the viscosity is called the fluidity, a measure of the ease of flow. Molasses, for example, has a greater viscosity than water. Because part of a fluid that is forced to move carries along to some extent adjacent parts, viscosity may be thought of as internal friction between the molecules; such friction opposes the development of velocity differences within a fluid. Viscosity is a major factor in determining the forces that must be overcome when fluids are used in lubrication and transported in pipelines. It controls the liquid flow in such processes as spraying, injection molding, and surface coating.

74. A particle of mass M initially at rest splits into two. If one of the particles of mass M1 moves with velocity V1 , the second particle moves with velocity

A. $\frac{M 1 V 1}{M - M 1}$

B. $\frac{M 1 V 1}{M 1 - M}$
C. $\frac{M 1 V 1}{M}$
D. $\frac{M V}{M - M 1}$

Correct Answer: Option B

75. To keep a vehicle moving at a constant speed V requires power P from the engine. The force provided by the engine is

A. $\frac{P}{v}$

B. ( $\frac{1}{2}$ )V
C. PV
D. $\frac{P}{V^{2}}$ $^{o}$

Correct Answer: Option A

Explanation

P = F ×

\frac{S}{1}

P = F x V
F =

\frac{P}{V}

^{o}

^{o}

^{o}

76. Which of the following is the dimension of pressure

A. ML $^{- 1}$ T $^{- 2}$

B. MLT

^{- 2}

C. ML

^{2}

^{3}

D. ML

^{- 3}

Correct Answer: Option A

Explanation

Pressure =

\frac{F o r c e}{A r e a}

Pressure = m ×

\frac{a}{t}

\frac{M L T^{- 2}}{L \times L}

= ML

^{- 1}

^{- 2}

77. Palm oil from a bottle flows out more easily after it has been heated because the

A. Molecules are given energy during the heating
B. Friction between oil layers is reduced
C. Oil molecules force each other out
D. Adhesion between the oil molecules and those of the bottle is increased

Correct Answer: Option B

Explanation

Molecules cannot be given energy during the heating and the molecules of oil cannot force each other out

78. A ball of mass 5.0kg hits a smooth vertical wall normally with a speed of 2ms

^{- 1}

. Determine the magnitude of the resulting impulse

A. 20.0kgms $^{- 1}$

B. 10.0kgms

^{- 1}

C. 5.0kgms

^{- 1}

D. 2.5kgms

^{- 1}

Correct Answer: Option B

Explanation

Impulse = Change in momentum
m (v - u)
5 (2.0)
= 5 x 2 = 10.0kgm

^{- 1}

= 10.0kgms

^{- 1}

79. The efficiency of energy conversion on the energy flow through a hydroelectric power is?

A. $\frac{E 1}{E 2}$

\frac{E 3}{E 2}

\frac{E 2}{E 1}

+ E2

\frac{E 2}{E 3}

+ E1

Correct Answer: Option B

Explanation

Efficiency =

\frac{useful energy output from machine}{energy input into machine}

\frac{E 3}{E 2}

80. An object weighs 30N in air and 21N in water. The weight of the object when completely immersed in a liquid of relative density 1.4 is

A. 25.2N
B. 17.4N
C. 12.6N
D. 9.0N

Correct Answer: Option B

Explanation

Weight of water displaced = upthrust = 30 - 21 = 9N
Mass of water displaced =

\frac{9}{10}

= 0.9kg
Volume of object = 9 × 10

^{- 4}

^{3}

= (9 × 10

^{- 4}

) (1.4 ×103)
= 1.26kg = 12N
30 - 12.6 = 17.4N

81. Which of the following instruments is most suitable for measuring the outside diameter of a narrow pipe in a few millimeters in diameter?

A. Pair of calipers
B. Meter rule
C. Micrometer screw gauge
D. Tape rule

Correct Answer: Option C

82. Electrical power is transmitted at a high voltage rather than a low voltage because the amount of energy loss is due to

A. Heat dissipation
B. Production of eddy currents
C. Excessive current discharge
D. Excessive voltage discharge

Correct Answer: Option A

Explanation

The primary reason that power is transmitted at high voltages is to increase efficiency. As electricity is transmitted over long distances, there are inherent energy losses along the way. High voltage transmission minimizes the amount of power lost as electricity flows from one location to the next. How? The higher the voltage, the lower the current. The lower the current, the lower the resistance losses in the conductors. And when resistance losses are low, energy losses are low also. Electrical engineers consider factors such as the power being transmitted and the distance required for transmission when determining the optimal transmission voltage

83. If the focal length of a camera is 20cm, the distance from the film at which the lens must be set to produce a sharp image of 100cm away is

A. 17cm
B. 20cm
C. 25cm
D. 100cm

Correct Answer: Option A

Explanation

F = 20cm
V = 100cm
U = ?

\frac{1}{U}

\frac{1}{V}

\frac{1}{F}

\frac{1}{20}

\frac{1}{100}

\frac{1}{F}

5 +

\frac{1}{100}

\frac{1}{F}

F =

\frac{100}{6}

= 16.7cm
= 17cm

84. The image of an object is located 6cm behind a convex mirror. If it's magnification is 0.6, calculate the focal length of the mirror

A. 3.75cm
B. 6.70cm
C. 10.00cm
D. 15.00cm

xplanation

V = 6cm
M = 6cm
Recall m = U =

\frac{V}{U}

U =

f r a c V M

=U =

\frac{6}{0.6}

U = 10

\frac{1}{U}

\frac{1}{V}

\frac{1}{F}

\frac{1}{10}

\frac{1}{6}

\frac{1}{F}

6 +

\frac{10}{60}

\frac{16}{60}

\frac{1}{F}

F =

\frac{60}{16}

= 3.75cm

85. A lens of focal length 15cm forms on erect image which is three times the size of the object. The distance between the object and the image is ___.

A. 10cm
B. 20cm
C. 30cm
D. 40cm

Correct Answer: Option D

Explanation

F= 15cm
M = 3
M =

\frac{v}{u}

V =3u

\frac{1}{f}

\frac{1}{u}

\frac{1}{v}

\frac{1}{15}

\frac{1}{u}

\frac{1}{3 u}

\frac{1}{15}

\frac{2}{3 u}

U =10cm
D = u + v
= 10 +30 = 40cm

86. The photo cell works on the principle of the

A. Voltaic cell
B. Emission of electron by incident radiation
C. Emission of protons by incident radiation
D. Photographic plate

Correct Answer: Option B

87. When a known standard resistor of 2.0 is connected to the 0.0cm end of a metre bridge, the balance point is found to be at 55.0cm

A. 1.10Ω
B. 1.64Ω
C. 2.44Ω
D. 27.50Ω

Correct Answer: Option B

Explanation

\frac{V_{1}}{V_{2}}

\frac{L_{1}}{(V_{2} - L_{1})}

\frac{R_{1}}{R_{2}}

\frac{L_{1}}{(V_{2} - L_{1})}

\frac{2}{R_{2}}

\frac{55}{45}

_{2}

= 2 ×

\frac{45}{55}

= 1.64Ω

88. A resistor connected to a 12V battery draws a current of 2A. The energy dispatched in the resistor in 5 minutes is ___.

A. 3,600J
B. 6,000J
C. 7,200J
D. 14,400J

Correct Answer: Option C

Explanation

Power drawn by the resistor = IV = (2)(3) = 24W = 24J/s
Energy dissipated = power × time = (24)(5)(60) = 7200J

89. A solid weighs 45N and 15N respectively in air and water. Determine the relative density of the solid

A. 0.33
B. 0.50
C. 1.50
D. 3.00

Correct Answer: Option D

Explanation

Weight in Air = 45N
Weight in Water = 15N
R.D =

\frac{Weight in Air}{Weight in water}

R.D =

\frac{45}{15}

= 3.00

90. A boy receives the echo of his clap reflected by a nearby hill 0.8s later. If the speed of sound in air is 3.40ms

^{-} 1

, how far is he from the hill?

A. 66m
B. 136m
C. 264m
D. 528m

Correct Answer: Option B

Explanation

Distance = speed × time
= (3400) × (0.812)
= 136m

91.The critical angle for light travelling from a transparent medium to air s measured as 340. The refractive index of the medium is

A. 0.56
B. 1.50
C. 1.79
D. 2.02

Correct Answer: Option C

Explanation

N =

\frac{1}{s i n θ}

\frac{1}{s i n 34}

= 1.79

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fortuneNovember 22, 2019 at 8:55 AM
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