JAMB UTME - Physics - 2018

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

Answer Details

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.

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

Answer Details

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.

Which of the following is the dimension of pressure

Answer Details

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.

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 ___.

Answer Details

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.

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

Answer Details

To make it easier understood
MA = E × Vr/100
Vr in a pulley system is the number of pulleys and in this case we have 5 (3 and 2)
So
MA = 72 × 5 = 360/100 = 3.6
Thanks

An object moves in a circular path of radius 0.5m with a speed of 1ms${}^{-1}$. What is its angular velocity?

Answer Details

Angular velocity is a measure of how fast an object is rotating around a center point. It's usually measured in radians per second (rad/s). To calculate angular velocity, we use the formula: angular velocity = linear velocity / radius. In this case, the linear velocity is 1 m/s, and the radius is 0.5 m. So, the angular velocity would be: 1 m/s / 0.5 m = 2 rad/s Therefore, the answer is 2 rad/s or 2rads^-1

Calculate the effective capacitance of the circuit in the diagram given

Answer Details

The three 2uf capacitors are in parallel to each other so u add them like this
2uf+2uf+2uf=6uf
So u have three capacitors in series
6uf 2uf and 3uf
They are in series so
1/C= 1/6+1/3=1/2
C=2uf
Then the same thing with the last two capay
1/2+1/2=1uf
Thanks

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

Answer Details

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.

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

Answer Details

The correct explanation for why a narrow beam of white light can be split up into different colors by a glass prism is that different colors of white light travel with different speeds in glass. White light is made up of different colors with different wavelengths, ranging from violet to red. When a narrow beam of white light passes through a glass prism, the different colors refract at slightly different angles due to the fact that their wavelengths are different. This causes the different colors to spread out and form a spectrum. The amount of refraction that occurs depends on the speed of light in the medium. Different colors of light have different speeds in glass due to the fact that their wavelengths are different. This means that they will refract at different angles as they pass through the glass prism, causing them to spread out. So, the correct explanation for why a narrow beam of white light can be split up into different colors by a glass prism is that different colors of white light travel with different speeds in glass. Therefore, is the correct explanation. is incorrect because it describes what white light is made up of, but does not explain how it is split up into colors by a prism. is incorrect because a prism does not have all the colors of white light, but rather it separates the colors that are already present in white light. is incorrect because total internal reflection occurs when light is completely reflected back into the same medium, which is not what happens when white light is split up by a prism.

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

Answer Details

The tendency of a body to remain at rest or to continue moving with a constant velocity (in a straight line at a constant speed) when no force is acting on it is called inertia. Inertia is a property of matter, and the amount of inertia depends on the mass of an object. Inertia can also be thought of as a resistance to changes in motion, meaning that an object at rest will tend to stay at rest, and an object in motion will tend to stay in motion unless acted upon by an external force. This property of inertia is what makes it difficult to start, stop, or change the direction of motion of an object. The force required to overcome the inertia of an object depends on the mass of the object and the magnitude of the acceleration desired. Therefore, the greater the mass of an object, the greater its inertia, and the more force required to change its motion.

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

Answer Details

Resolve vertically, 40cos? = 20, ? = 60${}^o$
Resolve horizontally, f = 40sin? = 40sin60${}^o$
= 40($\frac{\sqrt{3}}{2}$)
= 20?3 N

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

Answer Details

To find the moment of the force about point X, we need to first understand what moment is. Moment is the turning effect of a force around a pivot point. It is calculated by multiplying the force by the perpendicular distance between the pivot point and the line of action of the force. In this case, the force of 5N is acting on the rod at point Y. To find the moment of this force about point X, we need to find the perpendicular distance between point X and the line of action of the force. From the diagram, we can see that the perpendicular distance between point X and the line of action of the force is 2m (the length of the rod). So, the moment of the force about point X is: Moment = force x perpendicular distance = 5N x 2m = 10Nm Therefore, the correct answer is: 10Nm.

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

Answer Details

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.

A ball of mass 5.0kg hits a smooth vertical wall normally with a speed of 2ms${}^{?1}$. Determine the magnitude of the resulting impulse

Answer Details

The magnitude of the resulting impulse can be calculated using the formula impulse = change in momentum. In this scenario, the ball experiences a change in velocity (speed) as it hits the wall. The ball's initial momentum is equal to its mass times its velocity, and its final momentum is zero since it comes to a stop after hitting the wall. The change in momentum is equal to the final momentum minus the initial momentum, which is equal to the negative of the initial momentum. Since the ball has a mass of 5.0 kg and a velocity of 2 m/s, its initial momentum is 5.0 kg * 2 m/s = 10.0 kg m/s. Therefore, the change in momentum is -10.0 kg m/s and the magnitude of the resulting impulse is 10.0 kg m/s, which is equal to 10.0 Ns. So, the correct answer is 10.0kgms−1.

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

Answer Details

Neutron is not a product of nuclear fusion. Nuclear fusion is the process by which two or more atomic nuclei come together to form a heavier nucleus, releasing a large amount of energy in the process. In most fusion reactions, the resulting products are alpha particles (helium nuclei) and energy in the form of gamma rays. X-rays and gamma rays are both forms of high-energy electromagnetic radiation that can be produced by nuclear reactions, including nuclear fusion. Alpha particles are also a common product of nuclear fusion, especially in the fusion reactions that power the sun. However, neutrons are not typically produced in fusion reactions. In fact, one of the major challenges in developing fusion as a practical energy source is finding ways to produce and control the high-energy neutrons that are generated in the process. Neutrons can be produced in some types of fusion reactions, but they are not a primary product. In summary, neutron is not a product of nuclear fusion, while X-rays, Y-rays (assuming this is a valid form of radiation), and alpha particles are common products of this process.

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

Answer Details

X = $\frac{4}{3}$ r = ?
Shell?s law:. 7 = $\frac{Sin{2}^0}{Sin{r}^0}$
$\frac{V}{g}$ = $\frac{Sin{30}^0}{Sin{r}^0}$
Sin$r^0$ = $\frac{3Sin{30}^0}{4}$
Sin $r^0$ = 0.375
R ${}^o$ = Sin-1 (0.375)
R ${}^o$ = 22.02 ${}^o$
R ${}^o$ = 22 ${}^o$

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

Answer Details

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.

Answer Details

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

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

Answer Details

I think the correct option is C ($\frac{m_2}{m_1}$). The coefficient of friction is a ratio of two forces and hence g will cancel out.

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

Answer Details

Weight of water displaced = upthrust = 30 - 21 = 9N
Mass of water displaced = $\frac{9}{10}$ = 0.9kg
Volume of object = 9 × 10${}^{-4}$m${}^3$
= (9 × 10${}^{-4}$) (1.4 ×103)

 = 1.26kg = 12N
30 - 12.6 = 17.4N

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

Answer Details

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).

The photo cell works on the principle of the

Answer Details

The photocell works on the principle of the emission of electrons by incident radiation. In simple terms, a photocell is a device that converts light energy into electrical energy. It does this by using a material (such as silicon) that releases electrons when it is exposed to light. These electrons can then be collected and used to produce a current, which can be used to power an electrical device. The more light that hits the photocell, the more electrons are released and the greater the electrical current.

Convex mirrors are used as driving mirrors because images formed are

Answer Details

Convex mirrors are used as driving mirrors because the images formed by them are "erect, virtual, and diminished." Let me explain what these terms mean: - Erect: It means that the image appears upright, just like the actual object. This is important for a driving mirror because it allows the driver to perceive the correct orientation of the vehicles behind them. - Virtual: It means that the image appears to be behind the mirror, and not in front of it. This is also important for a driving mirror because it allows the driver to see a wider field of view without having to turn their head. - Diminished: It means that the image is smaller than the actual object. This is important for a driving mirror because it allows the driver to see a larger area behind them while still fitting it within the mirror's frame. Overall, these properties make convex mirrors ideal for use as driving mirrors as they provide the driver with an accurate view of the vehicles behind them without sacrificing their field of view.

What type of reaction is represented by the following scheme?

${}_1^{2}X$ + ${}_1^{2}Y$  -----> ${}_2^{3}Z$ + ${}_1^{0}n$ + energy

Answer Details

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.

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

Answer Details

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

Answer Details

F = 20cm
V = 100cm
U = ?
$\frac{1}{U}$ + $\frac{1}{V}$ = $\frac{1}{F}$
$\frac{1}{20}$ + $\frac{1}{100}$ = $\frac{1}{F}$
$\frac{5+1}{100}$ = $\frac{1}{F}$
F = $\frac{100}{6}$
= 16.7cm
= 17cm

The linear expansivity of brass is 2 x 10${}^{?5}$ C${}^{?1}$. If the volume of a piece of brass is 15.00cm at 0°C, what is the volume at 100°C

Answer Details

The linear expansivity of brass is given as 2 x 10^-5 /°C. This means that for every 1°C increase in temperature, the brass expands by 2 x 10^-5 of its original size. To find the new volume of the brass at 100°C, we need to take into account the expansion in all three dimensions (length, width, and height). Since the expansivity given is for length only, we need to find the expansivity in all three dimensions by multiplying it by 3. The expansivity in all three dimensions is: 3 x (2 x 10^-5 /°C) = 6 x 10^-5 /°C To find the new volume, we can use the formula: Vf = Vi (1 + αΔT) where Vf is the final volume, Vi is the initial volume, α is the expansivity in all three dimensions, and ΔT is the change in temperature. Plugging in the values, we get: Vf = 15.00 cm3 (1 + (6 x 10^-5 /°C) x (100°C - 0°C)) Vf = 15.09 cm3 Therefore, the volume of the brass at 100°C is 15.09 cm3.

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?

Answer Details

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 = $\frac{\text{MA}}{\text{VR}}\times 100\%$
$\text{MA}=\frac{\text{L}}{\text{E}},\text{VR}=n$
Efficiency = $\frac{\text{L}}{\text{E}}\times \frac{1}{\text{n}}\times 100\%$
$\text{E}=\frac{\text{L}}{\text{Eff.}\times n}\times 100\%$
$\text{E}=\frac{120\text{N}}{40\%\times 6}\times 100\%$
$\text{E}=50\text{N}$

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

Answer Details

The process by which protons are converted into helium atoms with a tremendous release of energy is called "thermonuclear fusion". In this process, two light atomic nuclei combine to form a heavier nucleus, releasing a huge amount of energy in the form of light and heat. This is the same process that powers the sun and other stars. The high temperatures and pressures required for fusion to occur can only be achieved in stars or in controlled environments such as fusion reactors. Thermonuclear fusion is different from nuclear fission, which is the process of splitting a heavy nucleus into lighter nuclei with the release of energy. Thermionic emission and photoelectric emission are different processes that involve the emission of electrons from a material due to heating or exposure to light, respectively.

The pitch of an acoustic device can be increased by

Answer Details

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".

In homes, electrical appliances and lamps are connected in parallel because

Answer Details

The density of 400cm3 of palm oil was 0.9gcm-3 before frying. If the density of the oil was 0.6gcm-3 after frying, assuming no loss of oil due to spilling, its new volume was?

Answer Details

The density of a substance is defined as its mass per unit volume. Therefore, the mass of the palm oil before frying was: Mass = Density x Volume = 0.9 g/cm³ x 400 cm³ = 360 g After frying, the mass of the palm oil remains the same, but its density changes to 0.6 g/cm³. Therefore, the new volume of the palm oil can be calculated by rearranging the density formula: Volume = Mass / Density = 360 g / 0.6 g/cm³ = 600 cm³ So the new volume of the palm oil after frying is 600 cm³. is the correct answer.

Which of the following obeys Ohm's law?

Answer Details

Ohm's law states that the current passing through a conductor is directly proportional to the voltage applied across it, given the temperature and other physical conditions remain constant. Among the given options, only "all metals" obey Ohm's law. This is because metals have a linear relationship between their resistance and the applied voltage, meaning that the resistance of a metal remains constant regardless of the voltage applied. As a result, the current passing through a metal is directly proportional to the voltage applied, following Ohm's law. On the other hand, a diode, all electrolytes, and glass do not obey Ohm's law. A diode is a semiconductor that has a non-linear current-voltage relationship, and its resistance is not constant. Similarly, electrolytes and glass are non-metallic substances that do not have a linear relationship between their resistance and the applied voltage. Their resistance can change significantly with the voltage applied, and hence they do not follow Ohm's law.

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

Answer Details

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.

Electrical appliances in homes are normally earthed so that

Answer Details

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.

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

Answer Details

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

What effort will a machine of efficiency 90% apply to a load of 180N if its efforts arm is twice as long as its load arm?

Answer Details

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

Answer Details

Efficiency = $\frac{\text{useful energy output from machine}}{\text{energy input into machine}}$
= $\frac{E3}{E2}$

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

Answer Details

The electrochemical equivalent of silver is a measure of the amount of silver that is deposited on a surface per unit of charge. In this case, the electrochemical equivalent of silver is 0.0012 grams per Coulomb of charge. To deposit 36.0 grams of silver by electrolysis, we need to know the amount of charge that must be passed through the solution. The amount of charge is given by: Q = m/z where m is the mass of silver to be deposited, 0.0012 is the electrochemical equivalent of silver, and z is the charge on one mole of electrons (z = 1 for a single electron). So, the amount of charge required is: Q = 36.0 g / 0.0012 g/C = 30000 C The current, I, is given by: I = Q / t where t is the time for which the current is flowing. In this case, t = 5 minutes. So, the current required is: I = 30000 C / (5 x 60 s) = 100 A Therefore, the current must be 100 Amperes.

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

Answer Details

A vernier caliper is a measuring device used to precisely measure linear dimensions. It is a very useful tool to use when measuring the diameter of a round objects like cylinders because the measuring jaws can be secured on either side of the circumference.
Vernier calipers have both a fixed main scale and a moving vernier scale. The main scale is graduated in either millimetres or tenths of an inch. The vernier scale allows much more precise readings to be taken (usually to the nearest 0.02mm or 0.001 inch) in comparison to a standard ruler (which only measures to th nearest 1mm or 0.25 inch).
The vernier scale was invented by French mathematician Pierre Vernier in 1631. As part of the vernier caliper, it is used together with the main scale, and helps to provide very precise measurements. Vernier calipers usually show either imperial or metric measurements, but some measure in both.