JAMB UTME - Physics - 2018
Pergunta 1 Relatório
Musical instruments playing the same note can be distinguished from one another owing to the difference in their
Detalhes da Resposta
Different musical instruments playing the same note can be distinguished from one another due to the difference in their "timbre" or "tone color." Timbre refers to the unique character or quality of a sound that allows us to distinguish it from other sounds even when they have the same pitch and loudness. For example, a piano and a guitar playing the same note will sound different due to the differences in their timbre. This is why we can tell the difference between different instruments and why some instruments are better suited to certain styles of music than others.
Pergunta 2 Relatório
When an atom loses or gain a charge it becomes
Detalhes da Resposta
When an atom loses or gains a charge, it becomes an ion. An ion is a type of atom that has an unequal number of protons and electrons, giving it a net electrical charge. If an atom loses one or more electrons, it becomes positively charged and is called a cation. On the other hand, if an atom gains one or more electrons, it becomes negatively charged and is called an anion.
So, in summary, an atom can lose or gain electrons to become an ion, which has a net electrical charge.
Pergunta 3 Relatório
One of the features of the fission process is that
Detalhes da Resposta
The fission process refers to the splitting of an atomic nucleus into two or more smaller nuclei. One of the key features of the fission process is that it can lead to a chain reaction, where the neutrons released during fission can go on to trigger additional fission reactions. This chain reaction can produce a large amount of energy, as is the case in nuclear power plants and nuclear weapons.
Another feature of the fission process is that it typically produces radioactive products. These products can remain radioactive for a long time, which is why there are concerns about the safe disposal of nuclear waste.
Additionally, the fission process typically releases neutrons, which can go on to cause further fission reactions. This neutron release is an important aspect of the chain reaction mentioned earlier.
Finally, the fission process is accompanied by a small loss of mass, which is converted into energy according to Einstein's famous equation E=mc². This loss of mass is what allows the large amount of energy to be released during a fission reaction.
Pergunta 4 Relatório
A room is heated by means of a charcoal fire, an occupants of the room standing away from the fire is warmed mainly by
Detalhes da Resposta
The main way that the occupants of a room standing away from a charcoal fire are warmed is by radiation. Radiation is the transfer of heat energy through electromagnetic waves, and it can travel through empty space.
In this scenario, the charcoal fire emits radiation in the form of infrared waves, which travel through the air and warm up the objects (including the occupants) in the room. Convection, on the other hand, is the transfer of heat through the movement of fluids (such as air), but in this case, the air in the room is not being actively circulated by a fan or other mechanism. Conduction involves the transfer of heat through direct contact between two objects, but the occupants are not in direct contact with the fire. Reflection refers to the bouncing of radiation off a surface, but it is not a significant factor in this scenario as most of the radiation is absorbed by the objects in the room.
Pergunta 5 Relatório
In homes, electrical appliances and lamps are connected in parallel because
Detalhes da Resposta
Pergunta 6 Relatório
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
Detalhes da Resposta
To determine the final temperature of the water, we can use the formula:
Q = mcΔT
where Q is the heat transferred, m is the mass of the water, c is the specific heat capacity of water, and ΔT is the change in temperature.
We know that the power of the electric heating coil is 1KW, which means it transfers 1000 Joules of energy per second. In 2 minutes, or 120 seconds, it transfers 120,000 Joules of energy to the water.
The mass of the water is given as 2kg and the specific heat capacity of water is 4000 J/kg°C. We can assume that the initial temperature of the water is 30°C.
Using the formula, we can solve for the change in temperature:
120,000 J = (2 kg)(4000 J/kg°C)(ΔT)
ΔT = 15°C
Therefore, the final temperature of the water is 30°C + 15°C = 45°C.
So, the final water temperature is 45.0oC.
Pergunta 7 Relatório
What flows to the earth by connecting the conductor to the earth?
Detalhes da Resposta
When a conductor is connected to the earth, electrons flow to the earth. Electrons are negatively charged particles that are present in all conductors. When a conductor is connected to the earth, it creates a path for electrons to flow from the conductor to the earth, which helps to balance the electric potential and prevent the buildup of electric charge. This flow of electrons is known as grounding and is an important safety measure in electrical systems.
Pergunta 8 Relatório
What type of reaction is represented by the following scheme?
\( {}_{1}^{2}X + {}_{1}^{2}Y \longrightarrow {}_{2}^{3}Z + {}_{1}^{0}n + \text{energy} \)
Detalhes da Resposta
The type of reaction represented by the given scheme is a nuclear fission reaction.
Nuclear fission is a process where a heavy nucleus is split into smaller nuclei with the release of energy. In the given scheme, a heavy element X is split into two lighter elements, Y and Z, along with the release of energy and some neutrons (n).
In a nuclear fission reaction, a neutron is usually absorbed by the nucleus of the heavy element, which then becomes unstable and splits into two smaller nuclei and some neutrons. These neutrons can then go on to split other heavy nuclei, resulting in a chain reaction.
In the given scheme, the release of energy and the presence of neutrons suggest that it is a fission reaction. Moreover, the scheme depicts the process of splitting a heavy element into two lighter elements, which is a characteristic of a fission reaction.
Therefore, the type of reaction represented by the given scheme is a nuclear fission reaction.
Pergunta 9 Relatório
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
Detalhes da Resposta
When a particle of mass M splits into two, the total mass is conserved, and so the sum of the masses of the two resulting particles must be equal to M. If one of the particles of mass M1 moves with velocity V1, we can use the law of conservation of momentum to determine the velocity of the second particle.
The law of conservation of momentum states that the total momentum of a system of particles remains constant if no external forces act on the system. In this case, the initial momentum of the system is zero, since the particle was initially at rest. After the particle splits, the momentum of the system is the sum of the momenta of the two resulting particles.
Let's use the subscript 1 to represent the first particle of mass M1 and the subscript 2 to represent the second particle of mass M-M1. By conservation of momentum, we have:
0 = M1*V1 + (M - M1)*V2
Solving for V2, we get:
V2 = -M1/M*(V1)
Therefore, the second particle moves in the opposite direction with velocity -M1/M*(V1). This means that the two particles move in opposite directions, with the ratio of their velocities determined by the ratio of their masses. Option (D) in the table shows the correct answer, which is -M1/M*(V1).
Pergunta 10 Relatório
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.
Detalhes da Resposta
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−1
V = 10ms−1
Change in momentum = m (v − u)
= 0.1 (10 − 2)
= 0.1 (8)
= 0.8Ns
Change in Momentum = Mass x (change in velocity)
Change in Momentum = Mass x (v - u)
Mass = 100g = 0.1kg
U = 2ms−1
V = 10ms−1
Change in momentum = m (v − u)
= 0.1 (10 − 2)
= 0.1 (8)
= 0.8Ns
Pergunta 11 Relatório
The time rate of loss of heat by a body is proportional to the
Detalhes da Resposta
The correct answer is "difference in temperature between the body and its surroundings."
When a body is at a higher temperature than its surroundings, it will lose heat to the surroundings until it reaches thermal equilibrium, i.e., until the temperatures of the body and its surroundings are equal. The rate at which the body loses heat is proportional to the temperature difference between the body and its surroundings. This is known as Newton's law of cooling.
The law of cooling applies to a wide range of situations, from the cooling of hot beverages to the cooling of electronic devices. It is important to understand this law because it allows us to predict how long it will take for a body to cool down to a certain temperature, and to design systems that can regulate the temperature of a body, such as heaters or refrigerators.
Pergunta 12 Relatório
Shadows and eclipses result from the
Detalhes da Resposta
The rectilinear propagation of light means that light travels in straight lines as a wave. This can be observed in the well-defined shadows formed when an object blocks a light source and through the use of a pinhole camera.
According to Sudipa Sarkar, the formation of shadows with sharp edges demonstrates the rectilinear propagation of light, i.e. The fact that light travels in straight line. When an opaque obstacle is placed between a source of light and a screen, a shadow of the obstacle is formed on the screen. The kind of shadow depends on the size of the source of light. If it is a point source (light from a small hole), the shadow obtained is a region of total darkness, called umbra.
If an extended source of light, e.g. a bulb, is used, the umbra is surrounded by a region of partial darkness, called penumbra. The moon is seen because it reflects the sun's light. An eclipse of the moon (lunar eclipse) occurs when the earth comes between the sun and the moon and prevents some of the light from the sun from reaching the moon. In other words, the earth casts its shadow on the moon. The solar eclipse occurs when the moon comes between the sun and the earth.
According to Sudipa Sarkar, the formation of shadows with sharp edges demonstrates the rectilinear propagation of light, i.e. The fact that light travels in straight line. When an opaque obstacle is placed between a source of light and a screen, a shadow of the obstacle is formed on the screen. The kind of shadow depends on the size of the source of light. If it is a point source (light from a small hole), the shadow obtained is a region of total darkness, called umbra.
If an extended source of light, e.g. a bulb, is used, the umbra is surrounded by a region of partial darkness, called penumbra. The moon is seen because it reflects the sun's light. An eclipse of the moon (lunar eclipse) occurs when the earth comes between the sun and the moon and prevents some of the light from the sun from reaching the moon. In other words, the earth casts its shadow on the moon. The solar eclipse occurs when the moon comes between the sun and the earth.
Pergunta 13 Relatório
Mercury which is spilled onto a glass surface forms ball-like shapes because____.
Detalhes da Resposta
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.
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.
Pergunta 14 Relatório
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
Detalhes da Resposta
X = 43
r = ?
Shell?s law:. 7 = Sin20Sinr0
Vg = Sin300Sinr0
Sinr0 = 3Sin3004
Sin r0 = 0.375
R o = Sin-1 (0.375)
R o = 22.02 o
R o = 22 o
Shell?s law:. 7 = Sin20Sinr0
Vg = Sin300Sinr0
Sinr0 = 3Sin3004
Sin r0 = 0.375
R o = Sin-1 (0.375)
R o = 22.02 o
R o = 22 o
Pergunta 15 Relatório
The differences observed in solids, liquids and gases may be accounted for by
Detalhes da Resposta
The differences observed in solids, liquids, and gases can be accounted for by the spacing and forces acting between the molecules.
In a solid, the molecules are packed closely together, so they have a fixed shape and volume. The intermolecular forces are strong enough to keep the molecules in a fixed position relative to one another.
In a liquid, the molecules are still close together, but they are free to move around each other. The intermolecular forces are weaker than in a solid, so the molecules can slide past one another, giving the liquid its ability to flow and take the shape of its container.
In a gas, the molecules are widely spaced and are in constant motion. The intermolecular forces are very weak, so the molecules are free to move around and fill any available space. Gases have no fixed shape or volume.
So, the differences observed in solids, liquids, and gases can be explained by the spacing and forces acting between the molecules. It's not about their relative masses, melting points, or the different molecules in each of them.
Pergunta 16 Relatório
A solid weighs 45N and 15N respectively in air and water. Determine the relative density of the solid
Detalhes da Resposta
The relative density of a substance is defined as the ratio of its density to the density of a reference substance, usually water at 4 degrees Celsius. In this problem, we can use the principle of buoyancy to determine the density of the solid. When an object is submerged in a fluid, it experiences an upward force called the buoyant force, which is equal to the weight of the fluid displaced by the object. If the object is less dense than the fluid, it will float, and if it is more dense, it will sink. We are given that the solid weighs 15 N in water, which means it displaces 15 N of water. The weight of the water displaced is equal to the buoyant force on the solid, which is equal to the weight of the solid when it is completely submerged in water. Therefore, the weight of the solid when it is completely submerged in water is 15 N. We are also given that the weight of the solid in air is 45 N. The difference between the weight of the solid in air and water is equal to the weight of the water displaced, which is 30 N. This means that the volume of water displaced by the solid is 30/9.8 = 3.06 L (since the density of water is 1000 kg/m^3 or 9.8 N/L). The relative density of the solid is equal to its density divided by the density of water. We can find the density of the solid by dividing its weight in air by its volume: Density of solid = Weight of solid in air / Volume of solid Density of solid = 45 N / (45 N - 15 N) [since weight of displaced water is 15N] Density of solid = 45 N / 30 N Density of solid = 1.5 N/L Therefore, the relative density of the solid is: Relative density = Density of solid / Density of water Relative density = 1.5 N/L / 1000 N/L Relative density = 0.0015 So the answer is 0.33 (rounded to two decimal places).
Pergunta 17 Relatório
Which of the following best describes the energy changes which take place when a steam engine drives a generator which lights a lamp?
Detalhes da Resposta
The energy changes that take place when a steam engine drives a generator which lights a lamp can be described as:
Heat energy from burning fuel is used to create steam in the boiler of the steam engine. This steam is then used to drive the turbine, which generates kinetic energy as it spins. The kinetic energy is transferred to the generator, which converts it into electrical energy (electricity). The electricity then flows through the wires to the lamp, where it is converted back into light energy, which is what we see.
Therefore, the correct option would be:
Heat ----> Kinetic ----> Electricity ----> Light
Pergunta 18 Relatório
Cathode rays are
Detalhes da Resposta
Cathode rays are streams of electrons. They were first discovered by scientists experimenting with vacuum tubes, and they observed that a glowing beam of particles traveled from the negatively charged electrode (the cathode) to the positively charged electrode (the anode). These particles were found to have a negative charge, which was later identified as electrons. Cathode rays played an important role in the development of electronics and the understanding of atomic structure.
Pergunta 19 Relatório
Which of the following is the dimension of pressure
Detalhes da Resposta
The dimension of pressure is ML-1T-2 Pressure is defined as the force per unit area. This means that pressure is dependent on the force applied and the area over which it is applied. The unit of force is measured in Newtons (N), and the unit of area is measured in square meters (m2). Therefore, the unit of pressure is N/m2, which is also known as Pascals (Pa). To determine the dimension of pressure, we need to break down the units into their fundamental dimensions of mass (M), length (L), and time (T). Force is measured in N, which is kg m/s2. Area is measured in m2, which is L2. Therefore, the dimension of pressure can be calculated as (kg m/s2)/(L2), which simplifies to ML-1T-2.
Pergunta 20 Relatório
The product of force and time is?
Detalhes da Resposta
The product of force and time is known as impulse.
Impulse can be defined as the change in momentum that an object experiences as a result of a force being applied to it over a period of time. In simpler terms, impulse is the "push" that an object receives from a force acting on it for a certain amount of time. The more force applied, or the longer the time the force is applied, the greater the impulse and the greater the change in momentum of the object.
It's important to note that impulse is a vector quantity, meaning it has both magnitude and direction. Impulse is a measure of the ability of a force to cause an object to change its velocity, and can be used to explain many phenomena in physics, such as why a heavy object is harder to stop than a lighter one, or why a soccer ball changes direction when it is kicked.
Pergunta 21 Relatório
Which of the following is true of an electrical charge?
Detalhes da Resposta
The correct answer is option D: "All of the above."
An electrical charge refers to the presence of an excess or deficit of electrons in an atom or molecule. In this context, positive charge means a deficit of electrons, whereas negative charge means an excess of electrons. Electric current refers to the flow of charged particles, typically electrons, through a conductor. Therefore, an electric current means the movement of electrons.
In summary, all of the given options are true of an electrical charge, and they all relate to the behavior of electrons in an electrically charged system.
Pergunta 22 Relatório
A resistor connected to a 12V battery draws a current of 2A. The energy dispatched in the resistor in 5 minutes is ___.
Detalhes da Resposta
To calculate the energy dispatched in the resistor, we need to use the formula:
Energy = Power x Time
Where Power is the amount of electrical power consumed by the resistor, and is equal to the product of the voltage across the resistor and the current flowing through it:
Power = Voltage x Current
In this case, the voltage across the resistor is 12V, and the current flowing through it is 2A. Therefore, the power consumed by the resistor is:
Power = 12V x 2A = 24W
Now, we can substitute this value of power along with the given time of 5 minutes into the formula for energy:
Energy = 24W x 5min x 60s/min = 7,200J
Therefore, the energy dispatched in the resistor in 5 minutes is 7,200J.
is the correct answer.
Pergunta 23 Relatório
Electrical appliances in homes are normally earthed so that
Detalhes da Resposta
Electrical appliances in homes are normally earthed so that a person touching the appliances is safe from electric shock. Earthing provides a safety mechanism by connecting the metal case of an electrical appliance to the earth through a conductor. In the event of a fault in the appliance, such as a short circuit, the current will flow through the earth wire instead of the person's body, preventing electric shock. By connecting the metal case of an appliance to the earth, the potential difference (PD) between the appliance and the earth is reduced to zero, ensuring that the appliance is maintained at a lower PD than the earth. Therefore, "the appliances are maintained at a lower pd than the earth" is the correct answer.
Pergunta 24 Relatório
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
Detalhes da Resposta
Weight of water displaced = upthrust = 30 - 21 = 9N
Mass of water displaced = 910
= 0.9kg
Volume of object = 9 × 10−4
m3
= (9 × 10−4
) (1.4 ×103)
= 1.26kg = 12N
30 - 12.6 = 17.4N
Pergunta 25 Relatório
In the diagram shown, which of the simple pendulum will resonate with P when set into oscillation?
Detalhes da Resposta
Pergunta 26 Relatório
The pitch of an acoustic device can be increased by
Detalhes da Resposta
The pitch of an acoustic device refers to the perceived highness or lowness of a sound, and is determined by the frequency of the sound wave. To increase the pitch of an acoustic device, you need to increase the frequency of the sound wave. This can be done by increasing the number of vibrations per second that the device produces.
So, the correct answer is to "increase the frequency".
Pergunta 27 Relatório
Which of the following instruments is most suitable for measuring the outside diameter of a narrow pipe in a few millimeters in diameter?
Detalhes da Resposta
The most suitable instrument for measuring the outside diameter of a narrow pipe in a few millimeters in diameter is a micrometer screw gauge.
A micrometer screw gauge is a precision measuring instrument that can accurately measure small dimensions with high accuracy. It has a spindle that moves towards an anvil and a scale that indicates the measurement. The spindle moves in response to a small rotation of the thimble, allowing for precise and sensitive measurements.
In contrast, a pair of calipers or a meter rule may not be accurate enough for measuring such small dimensions, and a tape rule may not be able to fit inside the narrow pipe. Therefore, a micrometer screw gauge is the most suitable option for measuring the outside diameter of a narrow pipe in a few millimeters in diameter.
Pergunta 28 Relatório
Which of the following phenomena is the practical evidence for the existence of the continual motion of molecules.
Detalhes da Resposta
Brownian motion is the practical evidence for the existence of the continual motion of molecules. This phenomenon is observed as the random movement of particles suspended in a fluid, such as a liquid or a gas, due to the constant bombardment of the fluid molecules. It was first described by the Scottish botanist Robert Brown in 1827 and provides strong evidence for the kinetic theory of matter, which states that all matter is made up of constantly moving particles. The random movement of the suspended particles can be observed through a microscope and is a direct result of the continual motion of the fluid molecules.
Pergunta 29 Relatório
The critical angle for light travelling from a transparent medium to air s measured as 340. The refractive index of the medium is
Detalhes da Resposta
The critical angle is the angle of incidence at which light is just able to pass through the interface between two media and not reflect back. When light travels from a medium with a higher refractive index to a medium with a lower refractive index, it slows down and bends towards the normal. If the angle of incidence is increased, the light will eventually reach a point where it will not be able to escape the higher index medium and will be totally reflected back. This is the critical angle.
The formula for the critical angle can be expressed as follows:
sin(θc) = n2/n1
Where θc is the critical angle, n1 is the refractive index of the first medium, and n2 is the refractive index of the second medium. In this case, the first medium is the transparent medium and the second medium is air, which has a refractive index of approximately 1.
By substituting the value of sin(θc) with the value of 340, and n2 with 1, we can solve for n1.
sin(340) = n1/1
n1 = 1/sin(340)
The value of n1 calculated using this formula is approximately 1.79, which means that the refractive index of the transparent medium is 1.79.
Pergunta 30 Relatório
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.
Detalhes da Resposta
The phenomenon of a mirage can be explained by options I and III. A mirage is an optical illusion that occurs when light rays passing through a medium with varying refractive indices create a false image of distant objects or even the sky. In hot weather, the air near the road surface becomes hotter and less dense than the air above, causing the light passing through it to bend and create a reflection of the sky or objects in the distance. This effect is known as a temperature inversion. Additionally, light from the sky can be reflected upwards after coming close to the road surface, adding to the illusion of a reflected object or the sky. Option II, which suggests that road surfaces become good reflectors in hot weather, is not a valid explanation for a mirage. Therefore, the correct answer is: I and III only.
Pergunta 31 Relatório
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?
Detalhes da Resposta
Let the total number of pulleys used in both the blocks be n
.
In a block-and-tackle pulley system, the velocity ratio is equal to n.
Efficiency = MAVR×100%
MA=LE,VR=n
Efficiency = LE×1n×100%
E=LEff.×n×100%
E=120N40%×6×100%
E=50N
In a block-and-tackle pulley system, the velocity ratio is equal to n.
Efficiency = MAVR×100%
MA=LE,VR=n
Efficiency = LE×1n×100%
E=LEff.×n×100%
E=120N40%×6×100%
E=50N
Pergunta 32 Relatório
Which of the following has the lowest internal resistance when new?
Detalhes da Resposta
Among the given options, the Accumulator has the lowest internal resistance when new.
Internal resistance is the resistance that a battery or cell provides to the flow of electric current within itself. Lower internal resistance means that the battery can supply more current to an external circuit without losing much of its own energy as heat.
An Accumulator, also known as a rechargeable battery, is designed to be charged and discharged multiple times. It has a relatively low internal resistance when new, meaning it can provide a higher current than the other cells listed while wasting less energy internally as heat.
A Leclanche cell and Daniell cell are primary cells, meaning they are designed to be used once and discarded. They have higher internal resistance compared to the accumulator, which limits their ability to supply high currents.
A Torch battery, also known as a dry cell, is also a primary cell and has a higher internal resistance than the accumulator. It is commonly used in small electronic devices and has a longer shelf life than Leclanche and Daniell cells.
In summary, an Accumulator has the lowest internal resistance when new, which makes it an ideal choice for applications requiring high current delivery such as electric vehicles, power tools, and renewable energy systems.
Pergunta 33 Relatório
The force between the molecules of a liquid in contact with that of a solid is?
Detalhes da Resposta
(ii) Adhesion : The force of attraction between unlike molecules, i.e. between the molecules of different liquids or between the molecules of a liquid and those of a solid body when they are in contact with each other, is known as the force of adhesion. This force enables two different liquids to adhere to each other or a liquid to adhere to a solid body or surface.
Pergunta 34 Relatório
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
Detalhes da Resposta
The correct answer is "I and III only".
Isotopes of an element have the same number of protons in their nuclei, meaning they have the same atomic number and are therefore the same element. Because of this, they have the same chemical properties.
However, isotopes of an element have different numbers of neutrons in their nuclei, which means they have different atomic masses. This is why isotopes can be separated using physical properties such as their mass or other characteristics related to their mass.
Pergunta 35 Relatório
An object is placed 20cm from a concave mirror of focal length 10cm. The linear magnification of the image produced is?
Detalhes da Resposta
The linear magnification of an image is given by the formula:
magnification = height of image / height of object = -v/u
where v is the image distance, u is the object distance, and the negative sign indicates that the image is inverted.
In this problem, the object is placed 20cm from a concave mirror of focal length 10cm. Since the object is placed beyond the focal point, the image will be real and inverted.
Using the mirror formula 1/f = 1/v + 1/u, we can find the image distance v:
1/10 = 1/v + 1/20
Solving for v, we get:
v = -20 cm
Now, we can use the magnification formula to find the linear magnification:
magnification = -v/u = -(-20)/20 = 1
Therefore, the linear magnification of the image produced is 1, which means the image is the same size as the object and is also inverted.
The answer is: 1.
Pergunta 36 Relatório
In the diagram given the hanging mass m2 is adjusted until m1 is on the verge of sliding. The coefficient of static
Detalhes da Resposta
I think the correct option is C (m2m1
). The coefficient of friction is a ratio of two forces and hence g will cancel out.
Pergunta 37 Relatório
A solid cube of side 50cm and mass 75kg floats in a liquid with \( \frac{1}{3} \) of its height above the liquid surface. The relative density of the liquid is?
Detalhes da Resposta
Volume of liquid displaced
= 23 (0.5)3
Mass of liquid displaced = mass of floating cube = 75kg
Density of liquid = massvolume
= 75(73(0.5)) × 3
= 0.9 × 103kgm−3
R.D of liquid = (0.9)(1.0) × 103
= 0.9
= 23 (0.5)3
Mass of liquid displaced = mass of floating cube = 75kg
Density of liquid = massvolume
= 75(73(0.5)) × 3
= 0.9 × 103kgm−3
R.D of liquid = (0.9)(1.0) × 103
= 0.9
Pergunta 38 Relatório
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 ___.
Detalhes da Resposta
We can use the lens formula, 1/f = 1/v - 1/u, where f is the focal length of the lens, v is the distance between the lens and the image, and u is the distance between the lens and the object.
From the problem, we know that the focal length of the lens is 15 cm, and the image is erect and three times the size of the object. This means that the image distance v is positive and the object distance u is negative (since the object is in front of the lens).
Let's assume that the object distance u is -x cm, where x is a positive number. Then, the image distance v is +3x cm, since the image is three times the size of the object. Substituting these values into the lens formula, we get:
1/15 = 1/(+3x) - 1/(-x)
Simplifying the right-hand side, we get:
1/15 = (1 + 3)/3x
Multiplying both sides by 3x, we get:
3x/15 = 4
Simplifying, we get:
x = 20
Therefore, the distance between the object and the lens is -20 cm (since it is in front of the lens), and the distance between the image and the lens is +60 cm (since it is behind the lens). The distance between the object and the image is the sum of these distances, which is:
(-20) + (+60) = 40 cm
Therefore, the answer is 40cm.
Pergunta 39 Relatório
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? \( \frac{1}{64} \)
Detalhes da Resposta
The half-life of a radioactive material is the time it takes for half of the atoms in a sample to decay. The fraction of atoms left after a certain number of half-lives can be calculated using the formula:
fraction left = (1/2)^(number of half-lives)
Let's use this formula to solve the problem. We know that the fraction of atoms left after 120 years is 1/64, which means that:
(1/2)^(number of half-lives) = 1/64
To solve for the number of half-lives, we can take the logarithm of both sides:
log[(1/2)^(number of half-lives)] = log(1/64)
Using the rule that log(a^b) = b*log(a), we can simplify the left side of the equation:
number of half-lives * log(1/2) = log(1/64)
Dividing both sides by log(1/2), we get:
number of half-lives = log(1/64) / log(1/2)
Using a calculator or the change of base formula, we can evaluate this expression:
number of half-lives = 6
Therefore, the half-life of the material is 120/6 = 20 years.
Pergunta 40 Relatório
In the diagram shown, If the south-poles of two magnets stroke a steel bar, the polarities at T and V will respectively be
Detalhes da Resposta
