JAMB UTME - Physics - 2019

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".

Which of the following statement about the electromagnet shown above is correct?

Detalhes da Resposta

A - B = S - N.
Also, starting end of the current is south while terminating end is North.

A coil X is moved quickly away from the end Y of a stationary metal bar and a current then flows in X as shown above.

Then

Detalhes da Resposta

N - S magnet is moved towards a coil production clockwise direction of current in the coil.
- This is the same as a coil moved away from S-N (Y - North pole)

- 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.

According to kinetic molecular model, in gases

Detalhes da Resposta

In kinetic molecular model, gases are energised and thus moves freely, fast as they occupy specific space

A boy pushes a 500kg box along a floor with a force of 2000N. If the velocity of the box is uniform, the co-efficient of friction between the box and the floor is

Detalhes da Resposta

The coefficient of friction is a measure of the amount of friction between two surfaces. It is represented by the symbol "μ" and is a dimensionless quantity. The coefficient of friction between two surfaces depends on the nature of the surfaces in contact and the force pressing them together. In this problem, the boy is pushing the box with a force of 2000N. If the box is moving with a uniform velocity, then the force of friction acting on the box is equal and opposite to the pushing force applied by the boy. We can calculate the force of friction using the formula: frictional force = coefficient of friction x normal force where the normal force is the force exerted by the floor on the box in a direction perpendicular to the floor. Since the box is not moving up or down, the normal force is equal to the weight of the box. The weight of the box can be calculated using the formula: weight = mass x gravity where mass is the mass of the box and gravity is the acceleration due to gravity (9.8 m/s^2). So, the weight of the box is: weight = 500 kg x 9.8 m/s^2 = 4900 N The force of friction is equal to the pushing force of 2000N, so we can set these two equal to each other and solve for the coefficient of friction: frictional force = 2000N coefficient of friction x normal force = 2000N coefficient of friction x 4900N = 2000N coefficient of friction = 2000N / 4900N = 0.408 So, the coefficient of friction between the box and the floor is approximately 0.4. Therefore, the correct answer is 0.4.

If the time of flight is 96seconds, calculate the horizontal range through the point of projection.

Detalhes da Resposta

Time of flight, T = 96s
R = (Ucosθ) *time* T = 640 × 96 = 61,440m

The equilibrium position of objects in any field corresponds to situation of

Detalhes da Resposta

The equilibrium position of an object in any field corresponds to the situation of minimum potential energy. This means that at the equilibrium position, the object has the lowest possible potential energy within the field. In other words, the forces acting on the object are balanced, and the object is not being pushed or pulled in any direction. Therefore, the object will remain at rest at the equilibrium position unless it is acted upon by an external force. Of the options given, the correct answer is "minimum potential energy".

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 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.

When a girl moves towards a plane mirror at a speed of 4.0m/s, the distance between the girl and her image reduces a speed of

Detalhes da Resposta

d = x, v = 4m/s
d = 2x, v = ? (girl and image)

The resultant capacitance in the figure above is

Detalhes da Resposta

For the parallel arrangement = 2 + 4 = 6μf

The height at which the atmosphere cases to exist is about 80km. If the atmospheric pressure on the ground level is 760mmHg, the pressure at a height of 20km above the ground level is

(ρm = 13.6g/cm${}^3$ ρ = 0.00013g/cm${}^3$ )

Detalhes da Resposta

ρ${}_m$h${}_m$ = ρ${}_a$h${}_a$
13.68(760 - p) × 10${}^{-3}$ = 13 × 10${}^{-5}$(20 × 10${}^3$)

760 - p = 190
p = 760 - 190 = 570mmHg

Workdone on an object to bring it to a certain point in space is called

Detalhes da Resposta

The work done on an object to bring it to a certain point in space is called "Potential Energy". Potential energy is a form of energy that an object possesses due to its position relative to other objects. When an object is lifted or moved to a higher point against gravity, work is done on it, and this work is stored as potential energy. The potential energy of an object is directly proportional to its height and mass. It can be converted into other forms of energy, such as kinetic energy, when the object is released or allowed to move freely. Therefore, potential energy is a type of stored energy that an object has due to its position, and it can be released to do work.

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.

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

If the attraction of the sun is suddenly ceased, the earth would continue to move in a straight line making a tangent with the original orbit. This statement is derived from Neutron's

Detalhes da Resposta

The correct answer is the First law of motion. The First law of motion, also known as the law of inertia, states that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force. In this case, the earth is moving in its orbit around the sun because of the force of gravity between the two objects. If the force of gravity suddenly ceased, the earth would no longer be acted upon by an external force and would continue to move in a straight line, making a tangent with its original orbit. This idea is attributed to Sir Isaac Newton, who developed the laws of motion and the law of universal gravitation. However, the specific statement mentioned in the question is derived from the First law of motion.

An a.c of 1A at a frequency of 800 cycles per second flows through a coil, the inductance of which is 2.5mH and the resistance of which is 5Ω. What is the power absorbed in the Coil?

Detalhes da Resposta

I = 1A, F = 800 cycles/s = 800Hz
R = 5Ω, L = 2.5mH
P = I${}^2$R = I${}^2$ × 5 = 5W

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.

When two objects A and B are supplied with the same quantity of heat, the temperature change in A is obtained to be twice that of B. The mass of P is half that of Q. The ratio of the specific heat capacity of A to B is

Detalhes da Resposta

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

Detalhes da Resposta

During the transformation of matter from the solid to the liquid state, the heat supplied does not produce a temperature increase because all the heat is used to break the bonds holding the molecules of the solid together

A body moves in SHM between two point 20m on the straight line Joining the points. If the angular speed of the body is 5 rad/s. Calculate its speed when it is 6m from the center of the motion.

Detalhes da Resposta

From two parts 20m apart
a = 10m, x = 6m, A = 5
V = ω$\sqrt{A^2-X^2}$  = 5$\sqrt{{10}^2-6^2}$ = 40m/s

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

The value of T in the figure above is

Detalhes da Resposta

Tsin30 + Tsin30 =40

2Tsin30 = 40

Tsin30 = 40/2 = 20

T($\frac{1}{2}$) = 20

T = 20 x 2 = 40N

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.

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 limiting frictional force between two surfaces depends on

I. the normal reaction between the surfaces

II. the area of surface in contact

III. the relative velocity between the surfaces

IV. the nature of the surfaces

Detalhes da Resposta

- Friction depends on the nature of the surfaces in contact
- Solid friction is independent of the area of the surfaces in contact and the relative velocity between the surfaces.

In a slide wire bridge, the balance is obtained at a point 25cm from one end of wire 1m long. The resistance to be tested is connected to that end and a standard resistance of 3.6$\Omega$ is connected to the other end of the wire. Determine the value of the unknown resistance

Detalhes da Resposta

$\frac{R}{3.6}=\frac{75}{25}=\frac{1}{3}$

3R = 3.6

R = 1.2$\Omega$

A straight wire 15cm long, carrying a current of 6.0A is in a uniform field of 0.40T. What is the force on the wire when it is at right angle to the field

Detalhes da Resposta

The force on a current-carrying wire in a uniform magnetic field can be calculated using the equation: F = BILsinθ where F is the force in Newtons, B is the magnetic field strength in Tesla, I is the current in Amperes, L is the length of the wire in meters, and θ is the angle between the wire and the magnetic field. In this problem, the wire is 15cm long (0.15m), carrying a current of 6.0A, and the magnetic field is 0.40T. The angle between the wire and the magnetic field is 90 degrees (since the wire is at right angles to the field). Substituting the given values into the equation, we get: F = (0.40T)(6.0A)(0.15m)sin90 sin90 = 1, so we can simplify the equation to: F = (0.40T)(6.0A)(0.15m) F = 0.36N Therefore, the force on the wire is 0.36N. Answer option C is the correct answer.

Any line or section taken through an advancing wave in which all the particles are in the same phase is called the

Detalhes da Resposta

The answer is: wave front. A wave front is any imaginary line or surface that connects all points of a wave that are in the same phase, meaning they are at the same point in their cycle. In other words, it is a line or surface that separates the points of a wave that are in-phase from those that are out-of-phase. For example, consider the ripples on the surface of a pond when a stone is thrown in. The wave fronts are the concentric circles that emanate from the point where the stone entered the water. All points along a given circle are in-phase, meaning the water molecules at those points are at the same point in their oscillation cycle. In summary, a wave front is a line or surface that separates points in a wave that are in-phase from those that are out-of-phase.

The statement 'Heat lost by the hot body equals that gained by the cold one' is assumed when determining specific that heat capacity by the method of mixtures. Which of the following validates the assumption?

I. Lagging the Calorimeter

II. Ensuring that only S.I units are used

III. Weighing the calorimeter, the lid and the stirrer.

Detalhes da Resposta

The assumption 'Heat lost by the hot body equals that gained by the cold one' is based on the law of conservation of energy, which states that energy cannot be created or destroyed, only transferred from one system to another. Thus, to validate this assumption, it's important to have a well-designed and insulated calorimeter so that as little heat as possible is lost to the environment. This is accomplished by lagging the calorimeter (Option I). Additionally, using the correct units (Option II) helps ensure that the energy transfer is accurately calculated and reported. Weighing the calorimeter, the lid, and the stirrer (Option III) is important for accurately measuring the amount of heat transferred, but by itself is not enough to validate the assumption. Therefore, the correct answer is "I and III only".

An alternating current can induce voltage because it has

Detalhes da Resposta

An alternating current can induce voltage because it has a varying magnetic field. An alternating current (AC) is an electrical current that periodically reverses direction, unlike direct current (DC), which flows in one direction. When an AC current flows through a wire, it generates a magnetic field that changes direction with the current. As the current alternates, the magnetic field expands and contracts, inducing an electromotive force (EMF) in any nearby conductor or coil of wire. This phenomenon is known as electromagnetic induction, and it is the basis for the operation of many electrical devices, such as generators and transformers. The induced voltage depends on the strength and rate of change of the magnetic field and the number of turns in the coil. In summary, an alternating current can induce voltage because it creates a varying magnetic field, which in turn generates an electromotive force in nearby conductors or coils of wire, according to the principle of electromagnetic induction.

A train has an initial velocity of 44m/s and an acceleration of -4m/s${}^2$. Calculate its velocity after 10 seconds

Detalhes da Resposta

The velocity of the train after 10 seconds can be calculated using the formula: v = u + at where v is the final velocity, u is the initial velocity, a is the acceleration, and t is the time. Substituting the given values, we get: v = 44 m/s + (-4 m/s^2) x 10 s v = 44 m/s - 40 m/s v = 4 m/s Therefore, the velocity of the train after 10 seconds is 4m/s. Answer option D is correct. Explanation: The train has an initial velocity of 44 m/s and an acceleration of -4 m/s^2. The negative sign indicates that the acceleration is in the opposite direction to the initial velocity, which means that the train is slowing down. After 10 seconds, the train's velocity decreases by 40 m/s (4 m/s^2 x 10 s) to reach a final velocity of 4 m/s.

Gases conduct electricity under

Detalhes da Resposta

Gases conduct electricity under low pressure and high voltage

Which of the following is/are the limitations to the Rutherford's atomic models?

I. It is applicable when energy is radiated as electrons are revolving

II. It is applicable when energy is radiated in a continuous mode

III. It is applicable to an atom with only one electron in the other shell

Detalhes da Resposta

Rutherford assumed that (I) energy is radiated when electrons are revolving (II) energy is radiated in a continuous mode. These are limitations of Rutherford's model

Lamps in domestic lightings are usually in

Detalhes da Resposta

Lamps in domestic lighting are usually connected in parallel. This means that each lamp is connected directly to the power supply, rather than being connected in a series or divergent or convergent configuration. In a parallel configuration, each lamp operates independently of the others, and if one lamp fails, the other lamps will continue to function. This is an important feature for domestic lighting, as it ensures that a single lamp failure will not leave the entire room in darkness. Additionally, in a parallel configuration, each lamp can be controlled independently, for example by a switch or dimmer, without affecting the operation of the other lamps. This allows for greater flexibility in lighting design and control. In summary, lamps in domestic lighting are usually connected in parallel because it allows for independent operation of each lamp and ensures that a single lamp failure does not affect the operation of the others.

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 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

The part of the human eye that does similar work as the diaphragm of a camera lens is the

Detalhes da Resposta

The part of the human eye that does similar work as the diaphragm of a camera lens is the iris. The iris is the colored part of the eye and is responsible for controlling the amount of light that enters the eye. Just like the diaphragm in a camera lens, the iris can adjust its size to allow more or less light into the eye. This helps to regulate the amount of light reaching the retina, which is responsible for sensing light and transmitting the image to the brain.

When water is boiling, it

Detalhes da Resposta

When water is boiling, it changes from a liquid state to a gaseous state called steam. This happens when the water is heated to its boiling point, which is when it reaches a temperature of 100 degrees Celsius (212 degrees Fahrenheit) at sea level. As the water is heated, it absorbs energy and the molecules start to move faster and faster, eventually reaching a point where they escape into the air as steam. The temperature of the water during boiling does not change, as all the energy is being used to break the bonds between the water molecules rather than increasing the temperature. Therefore, the options "gets hotter," "increase in mass," and "decreases in mass" are not correct when describing what happens when water is boiling.