JAMB UTME - Physics - 2019

The volume of 0.354g of helium at 273°C and 114cm of mercury pressure is 2667cm${}^3$. Calculate the volume

Detalhes da Resposta

m = 0.354g, T${}_1$ = 273°C = 273 + 273 = 576K
P${}_1$ = 114cmHg, V${}_1$ = 2667cm${}^3$ at STP
T${}^2$ = 273K, P${}_2$ = 76cmHg, V${}_2$ = ?

A cone is in unstable equilibrium has its potential energy

Detalhes da Resposta

In unstable equilibrium, potential energy decreases as the height decreases.

A body was slightly displaced from its equilibrium position. Which one of the following is a condition for its stable equilibrium

Detalhes da Resposta

The condition for stable equilibrium of a body that has been slightly displaced from its equilibrium position is "an increase in the potential energy of the body." When an object is at its equilibrium position, it has a minimum potential energy. When the object is displaced from its equilibrium position, it has a higher potential energy. For the object to be in stable equilibrium, it must be able to return to its equilibrium position after it has been displaced. If the potential energy of the object increases as it is displaced, it means that the equilibrium position is a point of stable equilibrium. This is because the object will experience a restoring force that will push it back towards its equilibrium position, as the potential energy decreases. Therefore, an increase in potential energy is a condition for a body to be in stable equilibrium after it has been slightly displaced from its equilibrium position. An increase in kinetic energy or height does not necessarily indicate stability, as it depends on the specific situation and other factors at play.

The point at which the molecules of a loaded wire begin to slide across each other resulting in a rapid increase in extension is

Detalhes da Resposta

The point at which the molecules of a loaded wire begin to slide across each other resulting in a rapid increase in extension is called the yield point. At this point, the material no longer behaves elastically and becomes permanently deformed. The yield point is an important parameter in material science and engineering as it indicates the maximum stress a material can withstand before it begins to deform plastically. Therefore, the yield point is a critical factor to consider when designing materials for specific applications.

The diagram above represents the stress-strain graph of a loaded wire. Which of these statements is correct?

Detalhes da Resposta

- I is the elastic limit
- the end of the constant part J is the yield point
- L is the break point.

Aluminium is sometimes used as the leaf of an electroscope because it

Detalhes da Resposta

- Aluminium can be made in thin sheet like Gold.
- the leaf is a thin material that can be diverged easily.

Which of the following readings cannot be determined with a meter rule?

Detalhes da Resposta

Meter rule has a reading accuracy of 0.5mm or 0.05cm, thus measurement is M ± 0.05cm i.e 2.00, 2.05, 2.50, 2.55 etc.
The reading that cannot be read is 2.56cm.

A supply of 400V is connected across capacitors of 3μf and 6μf in series. Calculate the charge

Detalhes da Resposta

= $\frac{18}{9}$ = 2μf
Q = CV
⇒ 2 × 10${}^{-6}$ × 400
⇒ 800 × 10${}^{-6}$C = 8 × 10${}^{-4}$C

Three resistors with resistance 200Ω, 500Ω and 1kΩ are connected in series. A 6v battery is connected to either end of the combination. Calculate the potential difference between the ends of 200Ω resistance.

Detalhes da Resposta

To calculate the potential difference between the ends of the 200Ω resistance, we need to use Ohm's Law, which states that the potential difference (V) across a resistor is equal to the current (I) flowing through the resistor multiplied by the resistance (R) of the resistor. First, we need to find the total resistance of the series combination of resistors. We add up the individual resistances: Total resistance = 200Ω + 500Ω + 1kΩ = 1.7kΩ Next, we can use Ohm's Law to find the current flowing through the circuit. We know that the battery voltage is 6V, and the total resistance is 1.7kΩ: I = V / R = 6V / 1.7kΩ = 0.0035A Now we can use Ohm's Law again to find the potential difference across the 200Ω resistor: V = IR = 0.0035A * 200Ω = 0.7V Therefore, the potential difference between the ends of the 200Ω resistance is 0.7V. The correct answer is option B.

In semi-conductor, the carriers of current at room temperature are

Detalhes da Resposta

In a semiconductor, the carriers of current at room temperature are both electrons and holes. Semiconductors are materials with properties that are in between those of conductors (e.g. metals) and insulators (e.g. rubber). At room temperature, a semiconductor crystal contains both free electrons and positively charged vacancies called holes. When a voltage is applied across the semiconductor, the electrons move towards the positive end of the circuit and the holes move towards the negative end. This movement of charge carriers constitutes an electric current. In summary, both electrons and holes can carry current in a semiconductor at room temperature, making the correct answer.

Which of the following media allow the transmission of sound waves through them?

I. air

II. liquid

III. solids

Detalhes da Resposta

Sound waves are disturbances in a medium that propagate through the medium and transfer energy from one point to another. The transmission of sound waves depends on the physical properties of the medium, including its elasticity and density. Air (Option I) is a gas that is compressible and has a relatively low density, which makes it an excellent medium for transmitting sound waves. Liquids (Option II) are also able to transmit sound waves, although the speed of sound in liquids is slower than in gases because liquids are more dense and less compressible. Solids (Option III) are able to transmit sound waves as well, but their density and elasticity make them more rigid, which means that sound waves in solids tend to be transmitted as elastic waves or mechanical waves, rather than as acoustic waves. Therefore, the correct answer is "I, II, and III".

A well 1km deep is filled with a liquid of density 950kg/m${}^3$ and g = 10m/s${}^2$, the pressure at the bottom of the well is

Detalhes da Resposta

P = Pa + ρgh = (1.00 × 10${}^5$) + (950 × 10 × 1000)
P = 10${}^5$ + (95 × 10${}^5$) = 10${}^5$(1 + 95) = 96 × 10${}^5$
P = 9.6 × 10${}^6$ N/m${}^2$

"Sum of all forces acting on a body is zero." This condition represents equilibrium'

Detalhes da Resposta

First condition

A microscope is focused on a mark on a table, when the mark is covered by a plate of glass 2m thick, the microscope has to be raised 0.67cm for the mark to be once more in focus. Calculate the refractive index.

Detalhes da Resposta

R = th = 2cm, d = 0.67cm

Gases conduct electricity under

Detalhes da Resposta

Gases conduct electricity under low pressure and high voltage

- angle of dip is zero at the magnetic equator
- angle of variation is the same as angle of declination.

Detalhes da Resposta

- angle of dip is zero at the magnetic equator
- angle of variation is the same as angle of declination.

A mass of 0.5kg is whirled in a vertical circle of radius 2m at a steady rate of 2 rev/s. Calculate the centripetal force

Detalhes da Resposta

The centripetal force is the force that acts towards the center and keeps an object moving in a circular path. To calculate the centripetal force, we can use the following formula: f = m * v^2 / r where: - f = centripetal force - m = mass of the object (0.5 kg) - v = velocity of the object (2 rev/s * 2 * pi m/rev = 12.57 m/s) - r = radius of the circle (2 m) Plugging in the values, we get: f = 0.5 kg * 12.57 m/s^2 / 2 m f = 31.43 N Rounding to the nearest whole number, the centripetal force is 31 N. So, the closest answer from the options is 160N.

When the temperature of a liquid is increased, its surface tension

Detalhes da Resposta

Surface tension or elasticity of a fluid decreases with increased in temperature

Calculate the velocity ratio of a screw jack of pitch 0.2cm if the length of the tommy bar is 23cm

Detalhes da Resposta

P = 0.2cm, L = r = 23cm

During the transformation of matter from the solid to the liquid state, the heat supplied does not produce temperature increase because

Detalhes da Resposta

When a solid is heated to its melting point, the heat supplied is used to overcome the intermolecular forces holding the molecules in a fixed position, resulting in the breaking of these bonds. As a result, the solid transforms into a liquid without any change in temperature. This is because the heat energy supplied is used in breaking the bonds between molecules rather than increasing the kinetic energy of the molecules, which is what causes an increase in temperature. Therefore, the correct option is: "all the heat is used to break the bonds holding the molecules of the solid together."

Which of the following is consistent with Charles' law?

I

II 

III

IV. 

Detalhes da Resposta

This is the correct graph. The graph is volume against 1/ temperature where temperature is in Celsius.

If a body moves with a constant speed and at the same time undergoes an acceleration, its motion is said to be

Detalhes da Resposta

If a body moves with a constant speed but at the same time undergoes an acceleration, its motion is called rectilinear motion. This means that the body moves in a straight line and its speed changes at a constant rate, causing an acceleration. It is different from oscillation, circular and rotational motions which involve changes in direction, as well as changes in speed.

The pin-hole camera produces a less sharply defined image when the

Detalhes da Resposta

The pin-hole camera produces a less sharply defined image when the pin-hole is larger. A pin-hole camera works by allowing light to pass through a small hole (the pin-hole) and project an inverted image of the outside world onto a screen or surface located behind the hole. The smaller the pin-hole, the sharper the resulting image, as light passing through a smaller hole produces less diffraction or spreading out of the light. When the pin-hole is larger, more light enters the camera, but the light rays also become more scattered, resulting in a less well-defined image. This is because the larger opening allows more light rays to enter at different angles, creating a wider range of paths that the light can take as it travels through the camera and onto the screen. As a result, the image is less clear and less defined, with less sharp edges and more blurring. is the correct answer because it correctly identifies the effect of a larger pin-hole on the image produced by the pin-hole camera. less illumination, would actually produce a dimmer image, but it would not affect the sharpness or definition of the image. the distance of the screen from the pin-hole, and the distance of the object from the pin-hole, would affect the size of the image and the scale of the objects, but they would not affect the sharpness or definition of the image.

A vibrator causes water ripples to travel across the surface of a tank. The wave travels 50cm in 2s and the distance between successive crests is 5cm. Calculate the frequency of the vibrator

Detalhes da Resposta

The frequency of the vibrator can be calculated using the formula: frequency = speed / wavelength where speed is the speed of the wave, and wavelength is the distance between successive crests. In this case, we are given that the wave travels 50cm in 2s, which means the speed of the wave is: speed = distance / time = 50cm / 2s = 25cm/s We are also given that the distance between successive crests is 5cm, which is the wavelength. Therefore, the frequency of the vibrator is: frequency = speed / wavelength = 25cm/s / 5cm = 5Hz So the correct answer is 5Hz.

The momentum of a car moving at a constant speed in a circular track

Detalhes da Resposta

Movement of an object in a circle with an acceleration towards its center is provided by change in velocity and centripetal force a α V α Fc

The diagram shows four positions of the bob of a simple pendulum. At which of these positions does the bob have maximum kinetic energy and minimum potential energy

Detalhes da Resposta

At position 1, the bob of the simple pendulum has the maximum potential energy and zero kinetic energy. At position 4, the bob has the maximum kinetic energy and minimum potential energy. To understand this, we need to know that the energy of a simple pendulum is converted back and forth between kinetic energy and potential energy as it swings back and forth. When the bob is at its highest point (position 1), it has the maximum potential energy because it is farthest from the ground and has the most potential to move downward. At this point, the bob has zero kinetic energy because it is momentarily at rest. As the bob swings downward towards the equilibrium point, it gains speed and its potential energy is converted to kinetic energy. At the equilibrium point (position 2), the bob has equal amounts of kinetic and potential energy. As the bob continues to move downward, its potential energy decreases and its kinetic energy increases. At position 3, the bob has minimum potential energy and some amount of kinetic energy. At the lowest point of its swing (position 4), the bob has maximum kinetic energy because it is moving at its fastest speed. At this point, the bob has minimum potential energy because it is closest to the ground and has the least amount of potential to move downward. So, to summarize, the bob has maximum potential energy at position 1, equal amounts of kinetic and potential energy at position 2, minimum potential energy at position 3, and maximum kinetic energy at position 4.

The distance between an object and its real image in a convex lens is 40cm. If the magnification of the image is 3, calculate the focal length of the lens

Detalhes da Resposta

u + v = 40

$\frac{v}{u}$ = 3

v = 3u

u + 3u = 40

4u = 40

u = 10cm

v = 3u = 30cm

f = $\frac{uv}{u+v}=\frac{10\left(30\right)}{10+30}=\frac{300}{40}$

= 7.5 cm

A car moving at 20m/s with its horn blowing (f = 1200Hz) is chasing another car going at 15m/s. What is the apparent frequency of the horn as heard by the driver being chased?

Detalhes da Resposta

The lead-acid accumulator consists of

Detalhes da Resposta

- the positive pole is lead peroxide (PbO${}_2$)
- the negative pole is head
- the electrolyte is H${}_2$SO${}_4$

Which of the following characteristics of a wave is used in the measurement of the depth of the Sea?

Detalhes da Resposta

Depth of sea can be measured by echo, a reflected sound waves.

The resultant capacitance in the figure above is

Detalhes da Resposta

For the parallel arrangement = 2 + 4 = 6μf

The following are parts of the eye

I. Retina

II. Pupil

III. Iris

The correct equivalent in the camera in the same order are

Detalhes da Resposta

- retina is similar to film
- pupil is similar to aperture
- iris is similar to diaphragm

Which of the following equations is the correct definition of the reactance of an indicator L?

Detalhes da Resposta

The correct definition of the reactance of an inductor L is: Reactance = (Amplitude of voltage) ÷ (Amplitude of current) The reactance of an inductor is a measure of the opposition offered by the inductor to the flow of alternating current (AC). It is denoted by the symbol Xl and is measured in ohms. When AC flows through an inductor, a magnetic field is generated around the inductor, which opposes any changes in the current flowing through it. This opposition to the flow of current is called reactance. The reactance of an inductor depends on its inductance, frequency of the AC signal, and the amplitude of the AC signal. However, the reactance of an inductor is directly proportional to the frequency of the AC signal and the inductance of the inductor. The reactance of an inductor is also affected by the amplitude of the AC signal, but this effect is not as significant as the other two factors. is the correct definition of the reactance of an inductor, as it expresses the ratio of the amplitude of voltage to the amplitude of current, which is a common way to define reactance. is incorrect, as it represents the power delivered by the AC signal, not the reactance. and are also incorrect, as they involve squaring either the amplitude of current or the amplitude of voltage, which is not a valid method of calculating reactance. Therefore, the correct option is.

Which of the following statements are correct of the production and propagation of waves?

I. vibration produces waves

II. waves transmit energy along the medium

III. the medium through which the wave travels does not travel with the wave

IV. waves do not require any medium for transmission

Detalhes da Resposta

The correct statement is: I and II and III only. Explanation: - Statement I is correct because the production of waves involves some kind of disturbance that creates a vibration in the medium, which then propagates as a wave. - Statement II is correct because waves carry energy along the medium as they propagate. This is why waves can be used to transmit information or power over long distances. - Statement III is correct because the medium through which a wave travels does not move with the wave. Instead, the wave passes through the medium, causing it to oscillate or vibrate, but not to move along with the wave. - Statement IV is incorrect because most waves require a medium through which to propagate. For example, sound waves require air, water waves require water, and seismic waves require the Earth's crust. There are some types of waves, such as electromagnetic waves, that can propagate through a vacuum, but this is not true for all waves.

The Earth's magnetic equator passes through Jos in Nigeria. At Jos, the

Detalhes da Resposta

The Earth has a magnetic field that is generated by the movement of molten iron in its core. The magnetic field has different properties at different locations on the Earth's surface. The magnetic equator is an imaginary line on the Earth's surface where the inclination or tilt of the Earth's magnetic field is zero, meaning that the magnetic field lines are parallel to the Earth's surface. At Jos, Nigeria, the Earth's magnetic equator passes through, which means that the angle of inclination or dip of the Earth's magnetic field is zero. Therefore, the correct answer is that the angle of dip is zero. This means that a magnetic needle suspended by a thread or placed on a horizontal surface would remain horizontal and not point downwards or upwards, as it would at other locations on the Earth's surface. This makes Jos an important location for studying the Earth's magnetic field and for conducting experiments related to magnetism.

The diagram shows a uniform meter rule AB which balances horizontally at the 90cm mark when a mass of 0.2kg is suspended from B. Calculate the mass of the meter rule.

Detalhes da Resposta

M${}_r$(90 - 50) = 0.2(100 - 90)
40M${}_r$ = 0.2 × 10

M${}_r$ = $\frac{2}{40}$ = 0.05kg

In Sunlight, a blue flower looks blue because we see the flower by the light it

Detalhes da Resposta

In sunlight, a blue flower looks blue because it reflects blue light. When sunlight falls on an object, the object can either absorb, transmit, or reflect the light. The color of an object that we see is determined by the light that is reflected by that object. For example, if an object appears blue, it is because it reflects blue light and absorbs other colors. In the case of a blue flower in sunlight, the petals of the flower reflect blue light and absorb other colors. This reflected blue light enters our eyes, and our brain interprets it as the color blue. Therefore, we see the blue flower as blue because it reflects blue light, and that is the color that enters our eyes. In summary, the reason why a blue flower looks blue in sunlight is that it reflects blue light and absorbs other colors.

A copper rod, 5m long when heated through 20c, expands by 1mm. If a second copper rod, 2.5m long is heated through 5c, by how much will it expand?

Detalhes da Resposta

l${}_1$ = 5m, ΔT = 10c, l${}_2$ - l${}_1$ = 1mm
l${}_1$  = 2.5m, ΔT = 5c, l${}_2$ - l${}_1$ = ?

A man on a bench will exert the greatest pressure on the bench when he

Detalhes da Resposta

The man on the bench will exert the greatest pressure when he stands on the toes of one foot. This is because when he stands on one foot, all his weight is concentrated on a smaller surface area of the bench, resulting in more pressure. The pressure he exerts is calculated by dividing his weight by the surface area in contact with the bench. When he stands on one foot, the surface area is smaller, which means the pressure exerted is greater. In comparison, when he lies flat on his back or belly, or when he stands on both feet, his weight is distributed over a larger surface area, resulting in less pressure.

The volume of a stone having an irregular shape can be determined using?

Detalhes da Resposta

The volume of a stone with an irregular shape can be determined using a measuring cylinder. A measuring cylinder is a glass or plastic container with a narrow cylindrical shape and markings on the side to indicate the volume it contains. To determine the volume of an irregularly shaped stone, you would fill the measuring cylinder with water, carefully lower the stone into the water, and note the increase in the volume of the water. The difference in the volume of the water before and after the stone was added is equal to the volume of the stone. The meter rule, vernier calliper, and micrometer screw gauge are all measuring instruments, but they are not designed to measure the volume of irregularly shaped objects. The meter rule is a measuring tool used for measuring length. The vernier calliper is used for measuring the diameter of objects, and the micrometer screw gauge is used for precise measurements of small distances.