JAMB UTME - Physics - 2020 | Green Bridge CBT

Question 1 Report

A substance has half of 3 min. After 6 min, the count rate was observed to be 400. What was its count rate at zero time?

1600

1200

200

2400

Answer Details

Let N = count rate at zero time

N 3min→ N 3min→ N

2 4

N

4

400

N = 400 x N

N/4

N = 1600

Read lesson note on Current Electricity (JAMB)

Current Electricity

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Question 2 Report

Consider the three forces acting at O and in equilibrium as shown in the figure. Which of the following equations is/are CORRECT?

I. $P_1 \sin \theta_1 = p_1 \cos \theta_2$

II. $P_3 = P_1 \cos \theta_4 + P_2 \cos_2$

III. $P_1 \sin \theta_1 = p_2 \sin \theta_2$

I only

ii only

iii only

I, II and III only

Answer Details

From ?ABC

P = P₁ cos ?

From $?$ ACD

P = P₂ cos?₂

P₁ cos ?₁

P₂Cos ?₂

Read lesson note on Equilibrium Of Forces (WAEC)

Equilibrium Of Forces

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Question 3 Report

In an experiment in which molten naphtha-line is allowed to cool, the cooling curve i n the figure was obtained. The temperature 80 $^{o}$ ⁰c is known as the

cooling temperature

boiling point

melting point

vaporization point

Temperature And Its Measurement

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Question 4 Report

What is the cost of running five 50W lamps and four 100W lamps for 10 hours if electrical energy costs 2 Kobo per KWh?

N0.65

N0.39

N3.90

N0.13

Answer Details

P = (5 x 50) + (100 x 4)

= 650watts

Energy(kWhr) = 650 x 10-3 x 10

= 6.5 kWhr

1kWhr cost 2 kobo ; 6.5 kWhr will cost 2×6.512×6.51

= 13 kobo

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Question 5 Report

The refractive index of a liquid is 1.5. If the velocity of light in a vacuum is 3.0 x 10

^{8} m s^{? 1}

, the velocity of light in the liquid is

1.5 x 10⁸ ms^-1

2.0 x 10⁸ ms^-1

3.0 x 10⁸ ms^-1

4.5 x 10⁸ ms^-1

Answer Details

The velocity of light in the liquid can be calculated using the formula for the refractive index (n) of a medium: v = c / n, where c is the velocity of light in a vacuum and n is the refractive index of the medium. In this case, n = 1.5, so the velocity of light in the liquid would be v = 3.0 x 10^8 m/s / 1.5 = 2.0 x 10^8 m/s. Therefore, the velocity of light in the liquid is 2.0 x 10^8 m/s

Read lesson note on Refraction Of Light Through Plane And Curved Surfaces (JAMB)

Refraction Of Light Through Plane And Curved Surfaces

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Question 6 Report

Natural radioactivity consists of emission___

α-particles and β-rays

α-particles and X-rays

ꝩ-rays and X-rays

α-particles and β-rays and ꝩ-rays

Answer Details

Solution

Radioactivity is the spontaneous emission of radiation from atomic nuclei. This radiation can consist of alpha, beta, and gamma radiation.

Natural radioactivity is a purely nuclear phenomenon. The nucleus of a radioactive substance is unstable and such an unstable nucleus undergoes spontaneous breakdown (disintegration). The process continues until a stable nucleus is obtained.

Read lesson note on Electromagnetic Field (Part 2) (WAEC)

Electromagnetic Field (Part 2)

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Question 7 Report

A machine gun with a mass of 5kg fires a 50g bullet at a speed of 100 ms

^{? 1}

. The recoil speed of the machine gun is

0.5 ms^-1

1.5 ms^-1

1 ms^-1

2 ms^-1

Answer Details

M_aV_a = M_bV_b

5 x V_a = 0.05 x 100

V_a = 1m⁻¹

Read lesson note on Work, Energy And Power (WAEC)

Work, Energy And Power

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Question 8 Report

A solid weighs 4.8g in air, 2.8g in water and 3.2g in Kerosine. The ratio of desity of the solid to that of the kerosine is

2

3

2

3

Time

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Question 9 Report

Which of the following instruments consumes the highest current?

I. Electric iron	250v	1kW
II. Television set	220v	110W
III. Torch light	6v	30W
IV.Immersion heater	110v	500W

i

ii

iii

iv

Current Electricity

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Question 10 Report

A convex mirror is used as a driving mirror because

I. its image is erect

II. It has a large field of view

III. It has a long focal length

Identify the CORRECT statement(s)

I and III only

I and II only

II and IIII only

I, II and III only

Answer Details

A) RT = 2 + 3 + 6 = 11Ω

(B) RT = 3×3 = 1.2Ω

2+3

(C) RT = 3×2×6

(2×3)+(2×6)+(3×6)

= 1Ω

(D) RT = 3 + 2×6

2+6

= 4.5 Ω

Read lesson note on Electrostatics (JAMB)

Electrostatics

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Question 11 Report

The linear expansivity of brass is 2 x 10

^{- 5}

-5

^{o} C^{- 1}

. If the volume of piece of brass is 2 x 10cm

^{3}

at 0

^{o}

C. What will be its volume at 100

^{o}

C?

10.06cm³

10.04cm³

10.02cm³

10.08 cm 3

Answer Details

3 x α = V₂−V₁

V1×Δθ

3 x 2 x 10⁻⁵ = V₂−10

100×10

V₂ = (100 x 10 x 3 x 2 10−2) + 10

= 10.6 cm³

Read lesson note on Temperature And Its Measurement (JAMB)

Temperature And Its Measurement

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Question 12 Report

A hydrometer is an instrument for measuring the

a depth of water of water in a vessel

relative density of a liquid by the method of flotation

relative density of a liquid by finding the apparent loss in weight

relative humidity of the air

Answer Details

A hydrometer is an instrument for measuring the relative density of a liquid by the method of flotation. A hydrometer works by measuring the weight of a liquid in relation to the weight of an equal volume of water. The relative density of a liquid can be determined by floating the hydrometer in the liquid and measuring the level at which it floats. The hydrometer is calibrated so that the level at which it floats indicates the relative density of the liquid. The relative density of a liquid is important because it can affect the behavior of the liquid, such as its ability to mix with other liquids, its ability to dissolve solids, and its behavior under different conditions, such as temperature and pressure. Understanding the relative density of a liquid is important in many industries, including the chemical, pharmaceutical, and food industries.

Read lesson note on Measurements And Units (JAMB)

Measurements And Units

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Question 13 Report

The mass of a proton is approximately equal to that of

an particle

a particle

a neutron

an electron

Answer Details

The mass of a proton is equal to that of the hydrogen atom. A hydrogen atom consists of one electron and one proton.

Read lesson note on Structure Of The Atom (Nigeria Only) (WAEC)

Structure Of The Atom (Nigeria Only)

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Question 14 Report

A few grains of table salt were put in a cup of cold water, kept at constant temperature and left undistributed. Eventually all the water tested salty. This action is due to?

convection

osmosis

capillarity

diffusion

Answer Details

Diffusion is the process by which molecules move from an area of higher concentration to an area of lower concentration until they are evenly distributed. It occurs in various substances, such as gases, liquids, and solids, and is driven by the random motion of molecules. This process plays a crucial role in many biological and physical phenomena, such as the movement of oxygen and carbon dioxide across cell membranes, the dispersion of perfume in the air, and the mixing of solutes in solutions.

Read lesson note on Electrostatics (JAMB)

Electrostatics

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Question 15 Report

One of the following readings represents the measurement of the measurement of the length of a metal rod using vernier callipers. Taking the reading accuracy into consideration, the most likely one is

5.165cm

A. 5.165cm

5.0cm

5.160cm

Answer Details

The most likely reading for the length of a metal rod using vernier callipers would be 5.160cm. This is because vernier callipers usually have a scale with increments of 0.1mm, and 5.160cm is the closest reading to 5.16cm, which would be the smallest increment that can be accurately measured using vernier callipers.
The other options, 5.165cm and 5.0cm, may not be as accurate as they do not match up with the smallest increment that can be measured using vernier callipers.

Read lesson note on Measurements And Units (JAMB)

Measurements And Units

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Question 16 Report

In what range of temperature is the expansion of water anomalous?

-208^oC + -212^oC

-80^oC + -76^oC

0^oC + 4^oC

-4^oC + 0^oC

Answer Details

The expansion of water is anomalous between 0°C to 4°C. This means that in this temperature range, the density of water actually decreases as the temperature increases. This is different from most substances, which typically become less dense when they are heated and expand. The anomalous behavior of water in this temperature range makes it a critical factor in many biological and physical processes on Earth.

Read lesson note on Temperature And Its Measurement (JAMB)

Temperature And Its Measurement

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Question 17 Report

The force required to make an object of mass m, travelling with velocity v, turn in a circle of radius r is

mV²

r

mr²

x

mr

v

mv

r²

Scalars And Vectors

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Question 18 Report

Two mirrors of the same length are arranges as show in the diagram. A ray of light NO strikes the system at O and emerges along PQ. The emergent ray has been deviated through

220⁰

200⁰

210⁰

180⁰

Answer Details

Angle of deviation = ?₁+?₂ = 50 + 50 + 40 + 40

= 180^o

Read lesson note on Electrostatics (JAMB)

Electrostatics

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Question 19 Report

Which of the following pairs is NOT part of the electromagnetic spectrum?

I. Radio waves

II. Beta rays

III. Gamma rays

IV. Alpha rays

I and II

III and IV

I and III

II and IV

Answer Details

The pair that is NOT part of the electromagnetic spectrum is IV. Alpha rays. The electromagnetic spectrum includes different types of electromagnetic radiation, such as radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays. Alpha rays are not part of this spectrum, but are instead a type of particulate radiation made up of helium ions. So the correct answer is "II and IV".

Read lesson note on Electromagnetic Waves: Types Of Radiation In Electromagnetic Spectrum (WAEC)

Read lesson note on Electromagnetic Field (Part 2) (WAEC)

Electromagnetic Waves: Types Of Radiation In Electromagnetic Spectrum

Electromagnetic Field (Part 2)

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Question 20 Report

The lower and upper fixed points marked on a Mercury-in-glass thermometer are 210mm. The end of the mercury column in the tube is 49mm above the lower fixed point in a room. What is the temperature of the room in degrees Celsius?

55.3⁰c

30.43⁰c

49.0⁰c

16.43⁰c

Answer Details

The temperature of the room in degrees Celsius is 30.43°C.
A Mercury-in-glass thermometer works by measuring the expansion of mercury in a glass tube as the temperature increases. The lower fixed point is typically the point where the mercury is at its minimum and the upper fixed point is where the mercury is at its maximum. In this case, the lower fixed point is at 0°C and the upper fixed point is at 30°C, and the mercury is 210mm above the lower fixed point. So, the temperature of the room must be 30.43°C.

Read lesson note on Temperature And Its Measurement (JAMB)

Temperature And Its Measurement

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Question 21 Report

Under which of the following conditions is work done?

A boy pushes unto a table

A stands on a table

A man supports a heavy food above his head with his hands

A woman holds a pot of water

Answer Details

Because work is done = force applied × distance.

Read lesson note on Work, Energy And Power (WAEC)

Work, Energy And Power

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Question 22 Report

If in a simple pendulum experiment the length of the inextensible string is increased by a factor or four, its period is increased by a factor of?

4

π

2

1

4

2

Answer Details

The period of a pendulum is the time it takes for one complete cycle of swinging back and forth. The period of a simple pendulum is determined by the length of the pendulum and the acceleration due to gravity. If the length of the pendulum is increased by a factor of four, then the period of the pendulum will also increase by a factor of two. This is because the period of a simple pendulum is proportional to the square root of its length. So, if the length of the pendulum is increased by a factor of four, the period will increase by a factor of the square root of four, which is equal to two. Therefore, the answer is 2.

Read lesson note on Equilibrium Of Forces (WAEC)

Equilibrium Of Forces

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Question 23 Report

Which of the following conditions are necessary and sufficient for total internal reflection to take place at the boundary between two optical media?

I. Light is passing from optical denser medium to optically less dense medium

II. Light is passing from optically less dense medium to optically denser medium to optically denser medium

III. Angle of incidence is greater

IV. Angle of incidence is lesser

I and II only

II only III only

III and IV only

I and III only

Electrostatics

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Question 24 Report

A transformer has 300 turns of wire in the primary coil and 30 turns in the secondary coil. If the input voltage is 100 volts, the input voltage is

5 volts

10 volts

15 volts

20 volts

Answer Details

The voltage in the secondary coil of a transformer is proportional to the ratio of the number of turns in the secondary coil to the number of turns in the primary coil. Since the secondary coil has 30 turns and the primary coil has 300 turns, the voltage in the secondary coil will be 1/10th of the voltage in the primary coil. Therefore, if the input voltage is 100 volts, the output voltage in the secondary coil would be 100 / 10 = 10 volts.

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Question 25 Report

The fiqure above 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 $^{o}$ , then the value of W is

28.0N

48.0N

288.0N

50.0N

Answer Details

V.E = 6, load = 120N

Efficiency = M.A x 1 x 100%

V.R

40 = 120 x 1 x 100

effort 6 1

Effort = 50N

Read lesson note on Scalars And Vectors (JAMB)

Scalars And Vectors

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Question 26 Report

In the study of Physics, temperature and heat are often confused with each other. Which of the following statements correctly defines these two elements?

Temperature is a measure of the average kinetic energy of the molecules of a substance

Heat is a measure of the total kinetic energy of the molecules in a system

Different materials require different amounts of heat to cause a given change in temperature

All of the above

Temperature And Its Measurement

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Question 27 Report

Which of the following statements about radioactivity is true?

(i) Alpha particle is positively charged

(ii) Beta particle is negatively charged

(iii) Gamma ray is neutral

(iv) Beta particle has the same mass as helium atom

(v) Gamma ray is charged.

i, ii, iii, iv only

i, ii, iii only

iv and v only

i, ii and v only

Answer Details

The correct answer is i, ii, iii only. Alpha particles are positively charged, beta particles are negatively charged, and gamma rays are neutral. Alpha particles are made up of two protons and two neutrons, while beta particles are high-energy electrons. Gamma rays are high-energy photons and have no charge. The mass of a beta particle is not the same as that of a helium atom. Gamma rays cannot be charged, as they are photons and photons are neutral.

Read lesson note on Electrostatics (JAMB)

Electrostatics

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Question 28 Report

The effect of closing the key K in the circuit shown in the figure above would be to?

increase the current by 0.4A

reduce the current by 0.4A

increase the current by 0.6A

reduce the current by 0.6A

Answer Details

When K is open, the total Resistance = 8 + 2 = 10?

1 = V? = 6v? = 0.6A

When K is closed, 18+18=1?

28=1?

? = 82 = 4?

4? in series with 2?= 6?

1 = V? = 66 = 1A

1 - 0.6A = 0.4A

Hence, 0.4A increase

Read lesson note on Capacitors (JAMB)

Capacitors

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Question 29 Report

A ship travelling towards a cliff receives the echo of its whistle receives the echo of its whistle after 3.5 seconds. If the speed of sound in air under the prevailing conditions is 250ms

^{- 1}

, how much closer is the ship to the cliff?

10m

A. 350m

175m

125m

Answer Details

Difference in time = 1 sec

Echo time = 1 $\div$ / 2 = 0.5 sec

Difference of cliff from ship = 0.5 x 250

= 125m

Read lesson note on Electric Field (WAEC)

Read lesson note on Change Of State (JAMB)

Electric Field

Change Of State

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Question 30 Report

Two drivers G and H are at depths 20m and 40m, respectively below the water surface in a lake. The pressure on G is O1

_{1}

while the pressure on H is P

_{2}

, If the atmospheric pressure is equivalent to 10m²

^{2}

of water, then the value of P1

_{2}

/P

_{1}

2 is

0.50

0.60

1.67

2.00

Answer Details

The pressure at a depth h below the surface of a liquid can be calculated using the equation: P = P_atmosphere + ρgh where P_atmosphere is the atmospheric pressure, ρ is the density of the liquid, g is the acceleration due to gravity, and h is the depth below the surface. Given that the atmospheric pressure is 10m^2, the pressure at a depth of 20m and 40m below the surface of the lake would be: P1 = 10 + ρgh = 10 + 1000 * 9.8 * 20 = 10 + 1960 P2 = 10 + ρgh = 10 + 1000 * 9.8 * 40 = 10 + 3920 So, P2 / P1 = 3920 / 1960 = 2.00 Therefore, the value of P2 / P1 2 is 2.00.

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Question 31 Report

Which of the following statements about defects of vision is/are CORRECT?

I. For a long sighted person, close objects appear blurred

II. For a short sighted person, distant objects appear blurred

III. Short sight is corrected by using a pair of converging lenses

I only

II only

I and II only

II and III only

Equilibrium Of Forces

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Question 32 Report

A magnetic needle is suspended first at the earth's north magnetic pole and then at a point on the magnetic equator. The respective angles between the needle and the horizontal are

0⁰ and 0⁰

60⁰ and 60⁰

90⁰ and 90⁰

90⁰ and 0⁰

Magnets And Magnetic Fields

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Question 33 Report

Which of the following can be described as high tension transmission?

High resistance and low voltage

Low current and high voltage

High current and low voltage

High current and low resistance

Answer Details

High tension transmission refers to the transmission of electrical power at high voltage levels. High voltage allows for the transmission of electrical power over long distances with reduced losses, as less current is needed to transmit the same amount of power at high voltage. Therefore, high tension transmission can be described as high voltage and low current. This corresponds to: Low current and high voltage. In contrast, low tension transmission refers to the transmission of electrical power at low voltage levels, typically in the range of 110-240 volts. This type of transmission typically requires higher current levels to transmit the same amount of power.

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Read lesson note on Liquids At Rest (JAMB)

Electric Field

Induction

Liquids At Rest

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Question 34 Report

Heat is supplied uniformly at the rate of 100W to 1.0 x 10^-2 kg of a liquid for 20 seconds. If the temperature of the liquid rises by 5

^{o}

⁰c, then the specific heat capacity of the liquid is

2.5 x 10² jkgk^? 1K^- 1

2.0 x 10² jkg^? 1

4.0 x 10⁴ jkgk^? 1K^- 1

4.0 x 10⁴ jkg^? 1

Answer Details

Heat energy = Electrical Energy

Hence,

MCθ = power x time

5 x 1 x 10⁻² x C = 100 x 20

C = 200

5×10²

= 4 x 10⁴ J/kg/^oC

Read lesson note on Heat Energy (WAEC)

Heat Energy

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Question 35 Report

If a source of solid is moving, a stationary listener will hear a sound of different frequency. This is called?

doppler effect

resonance

ultra sound

rarefaction

Answer Details

The phenomenon you're referring to is known as the Doppler effect. Simply put, the Doppler effect is a change in the frequency of a wave (such as sound or light) as the source of the wave moves relative to an observer. For example, if a car is approaching you, the sound of its horn will seem to have a higher frequency (or pitch) than if it were stationary or moving away from you. This is because as the car moves towards you, the sound waves are compressed, causing an increase in the frequency that you hear. Conversely, if the car is moving away from you, the sound waves will be stretched out, causing a decrease in the frequency that you hear. This is why the sound of a siren on an ambulance moving away from you seems to get lower and lower as it gets further away. So in short, the Doppler effect is a change in the frequency of sound (or any other wave) that occurs when the source of the wave is moving relative to an observer.

Read lesson note on Sound Waves (WAEC)

Sound Waves

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Question 36 Report

Which of the following statements on the use of X-rays is incorrect? X-rays are used

In a hospital to obtain photographs of tissues and bones in the body

For the treatment of malignant growths like cancer cells

In detecting fingerprints

To reveal hidden flaws in metal castings and welded joints work of art

Answer Details

The statement that is incorrect is "In detecting fingerprints". X-rays are not used for detecting fingerprints. X-rays are used for obtaining images of tissues and bones inside the body, for the treatment of malignant growths like cancer cells, and to reveal hidden flaws in metal castings and welded joints in works of art. Fingerprints are usually detected using techniques like fingerprint scanning or live-scan biometrics.

Read lesson note on Structure Of The Atom (Nigeria Only) (WAEC)

Structure Of The Atom (Nigeria Only)

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Question 37 Report

In the figure, the value of R is

3Ω

6Ω