JAMB UTME - Physics - 2018
Swali 1 Ripoti
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
Maelezo ya Majibu
Swali 2 Ripoti
A 40W instrument has a resistance 90 Ohms. On what voltage should it be operated normally
Maelezo ya Majibu
To calculate the voltage needed for a 40W instrument with a resistance of 90 Ohms, we can use the formula:
Voltage = √(Power x Resistance)
Plugging in the given values, we get:
Voltage = √(40W x 90Ω)
Voltage = √(3600)
Voltage = 60V
Therefore, the instrument should be operated at 60V to generate 40W of power with a resistance of 90 Ohms. The correct answer is, 60V.
Swali 3 Ripoti
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
Maelezo ya Majibu
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.
Swali 4 Ripoti
A narrow beam of white light can be split up into different colours by a glass prism. The correct explanation is that
Maelezo ya Majibu
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.
Swali 5 Ripoti
A resistor connected to a 12V battery draws a current of 2A. The energy dispatched in the resistor in 5 minutes is ___.
Maelezo ya Majibu
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.
Swali 6 Ripoti
The resistance of a 40W car head lamp, drawing current from a 12V battery is ____.
Maelezo ya Majibu
The resistance of a 40W car headlamp can be calculated using Ohm's Law, which states that the current (I) flowing through a conductor between two points is directly proportional to the voltage (V) across the two points, and inversely proportional to the resistance (R) of the conductor. The equation can be written as V = IR.
Since the power (P) of the headlamp is given as 40W and the voltage is 12V, we can calculate the current using the equation P = IV. Substituting I = P/V, we get I = 40/12 = 3.33A.
Finally, using Ohm's Law, we can calculate the resistance as R = V/I = 12/3.33 = 3.6Ω.
So, the resistance of the 40W car headlamp, drawing current from a 12V battery, is 3.6Ω.
Swali 7 Ripoti
Electrical appliances in homes are normally earthed so that
Maelezo ya Majibu
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.
Swali 8 Ripoti
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? \( \frac{1}{64} \)
Maelezo ya Majibu
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.
Swali 9 Ripoti
A ball of mass 800g moving horizontally with a speed of 5m/s hits a vertical wall and rebounds with the same speed. The impulse experienced by the ball is?
Maelezo ya Majibu
The impulse experienced by the ball can be calculated using the principle of conservation of momentum, which states that the total momentum before the collision is equal to the total momentum after the collision. In this case, the momentum of the ball before the collision is:
p1 = m * v1
where m is the mass of the ball and v1 is its velocity before the collision. Substituting the values given in the problem, we get:
p1 = 0.8 kg * 5 m/s = 4 kg m/s
After the collision, the ball rebounds with the same speed but in the opposite direction, so its velocity after the collision is:
v2 = -5 m/s
The momentum of the ball after the collision is:
p2 = m * v2
Substituting the values, we get:
p2 = 0.8 kg * (-5 m/s) = -4 kg m/s
The negative sign indicates that the direction of the momentum is opposite to that before the collision.
The change in momentum of the ball is given by:
Δp = p2 - p1
Substituting the values, we get:
Δp = (-4 kg m/s) - (4 kg m/s) = -8 kg m/s
The negative sign indicates that the impulse experienced by the ball is in the opposite direction to its initial momentum, which is the direction of the wall. Therefore, the impulse experienced by the ball is 8 kg m/s.
Therefore, the correct option is: 8kgm/s.
Swali 10 Ripoti
A ball of mass 5.0kg hits a smooth vertical wall normally with a speed of \(2\text{ms}^{-1}\). Determine the magnitude of the resulting impulse
Maelezo ya Majibu
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.
Swali 11 Ripoti
Which of the following phenomena is the practical evidence for the existence of the continual motion of molecules.
Maelezo ya Majibu
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.
Swali 12 Ripoti
Which of the following instruments is most suitable for measuring the outside diameter of a narrow pipe in a few millimeters in diameter?
Maelezo ya Majibu
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.
Swali 13 Ripoti
One of the features of the fission process is that
Maelezo ya Majibu
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.
Swali 14 Ripoti
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 ___.
Maelezo ya Majibu
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.
Swali 15 Ripoti
In the diagram shown, which of the simple pendulum will resonate with P when set into oscillation?
Maelezo ya Majibu
Swali 16 Ripoti
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?
Maelezo ya Majibu
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
Swali 17 Ripoti
The linear expansivity of brass is \(2 \times 10^{-5}\,\text{C}^{-1}\). If the volume of a piece of brass is 15.00cm at 0°C, what is the volume at 100°C
Maelezo ya Majibu
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.
Swali 18 Ripoti
In the diagram given the hanging mass m2 is adjusted until m1 is on the verge of sliding. The coefficient of static
Maelezo ya Majibu
I think the correct option is C (m2m1
). The coefficient of friction is a ratio of two forces and hence g will cancel out.
Swali 19 Ripoti
Convex mirrors are used as driving mirrors because images formed are
Maelezo ya Majibu
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.
Swali 20 Ripoti
Which of the following is an essential physical property of the wires uses for making fuses ?
Maelezo ya Majibu
The essential physical property of the wire used for making fuses is low melting point. This means that the wire should have a low temperature at which it melts and breaks, interrupting the flow of electrical current. This is important in a fuse because when there is an overload of electrical current, the wire will melt, breaking the circuit and preventing damage to the electrical system.
The other options, low density, low electrical resistivity, and hypothermal conductivity, are not as important for a fuse wire. Low density is the property of a material to be light, and it doesn't necessarily affect the performance of a fuse wire. Low electrical resistivity is the property of a material to have low resistance to the flow of electrical current, and it doesn't necessarily affect the performance of a fuse wire either. Hypothermal conductivity is the property of a material to conduct heat poorly, and it also doesn't necessarily affect the performance of a fuse wire.
Swali 21 Ripoti
Palm oil from a bottle flows out more easily after it has been heated because the
Maelezo ya Majibu
Molecules cannot be given energy during the heating and the molecules of oil cannot force each other out
Swali 22 Ripoti
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
Maelezo ya Majibu
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
Swali 23 Ripoti
The energy needed to move a unit positive charge around a complete electric circuit is called the
Maelezo ya Majibu
The energy needed to move a unit positive charge around a complete electric circuit is called the "electromotive force", also known as "emf". This is because the emf is what drives the flow of electric charge, or current, around the circuit.
Think of it like a battery in a flashlight. The battery provides the emf that drives the flow of electric current through the wires and the light bulb. Without the emf from the battery, the electric charges wouldn't be able to flow and the light wouldn't turn on.
The other answer options, such as electric potential difference and electric energy, are related to the emf but don't specifically refer to the energy needed to move a unit positive charge around a circuit. Kinetic energy, on the other hand, is not related to the movement of electric charges around a circuit at all.
Swali 24 Ripoti
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?
Maelezo ya Majibu
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.
Swali 25 Ripoti
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?
Maelezo ya Majibu
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.
Swali 26 Ripoti
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.
Maelezo ya Majibu
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
Swali 27 Ripoti
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
Maelezo ya Majibu
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.
Swali 28 Ripoti
A boy receives the echo of his clap reflected by a nearby hill 0.8s later. If the speed of sound in air is 3.40ms\(^{-1}\), how far is he from the hill?
Maelezo ya Majibu
The speed of sound in air is given as 3.40 m/s. The echo of the clap is heard 0.8 seconds after it was produced, which means it traveled to the hill and back. The time taken for sound to travel to the hill is half of the time taken for it to travel to and from the hill. Therefore, the time taken for sound to travel to the hill is 0.8/2 = 0.4 seconds.
We can use the formula:
distance = speed x time
to calculate the distance between the boy and the hill.
distance = speed of sound x time taken for sound to travel to the hill
distance = 3.40 m/s x 0.4 s
distance = 1.36 m
Therefore, the distance between the boy and the hill is 1.36 meters.
However, the answer options provided are in meters and are significantly larger than 1.36 meters. It is possible that the speed of sound provided in the question is incorrect or the answer options are incorrect.
Swali 29 Ripoti
Which of the following is the dimension of pressure
Maelezo ya Majibu
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.
Swali 30 Ripoti
Which of the following is not a product of nuclear fusion?
Maelezo ya Majibu
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.
Swali 31 Ripoti
The product of force and time is?
Maelezo ya Majibu
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.
Swali 32 Ripoti
The force between the molecules of a liquid in contact with that of a solid is?
Maelezo ya Majibu
(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.
Swali 33 Ripoti
The critical angle for light travelling from a transparent medium to air s measured as 340. The refractive index of the medium is
Maelezo ya Majibu
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.
Swali 34 Ripoti
Water of mass 150g at \(60^\circ\)c is added to 300g of water at \(20^\circ\)c and the mixture is well stirred. Calculate the temperature of the mixture.(neglect heat losses to the surroundings)
Maelezo ya Majibu
To solve this problem, we can use the principle of conservation of energy, which states that energy cannot be created or destroyed, only transferred or converted from one form to another. In this case, the energy transferred is in the form of heat.
We can use the formula:
Q = m*c*(ΔT)
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.
First, we can calculate the heat transferred from the hot water to the cold water:
Q1 = 150g * 4.18 J/(g°C) * (60°C - T)
Q1 = 627 * (60 - T)
where T is the temperature of the mixture.
Next, we can calculate the heat transferred from the cold water to reach the final temperature of the mixture:
Q2 = 300g * 4.18 J/(g°C) * (T - 20°C)
Q2 = 1254 * (T - 20)
Since the heat transferred between the two water samples must be equal, we can set Q1 equal to Q2 and solve for T:
627 * (60 - T) = 1254 * (T - 20)
37620 - 627T = 1254T - 25080
1881T = 62760
T = 33.4°C
Therefore, the temperature of the mixture is approximately 33°C.
Answer: 33°C
Swali 35 Ripoti
The time rate of loss of heat by a body is proportional to the
Maelezo ya Majibu
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.
Swali 36 Ripoti
When a known standard resistor of 2.0 is connected to the 0.0cm end of a meter bridge, the balance point is found to be at 55.0cm. What is the value of the unknown resistor?
Maelezo ya Majibu
A meter bridge is an instrument used to measure the unknown resistance of a conductor. The meter bridge consists of a long resistance wire AB of uniform cross-sectional area and a battery of known voltage connected across its ends. A galvanometer is connected across a point C on the wire, which is called the null point or balance point.
When a known standard resistor of 2.0 ohms is connected to the 0.0cm end of the meter bridge wire, the balance point is found to be at 55.0cm. This means that the resistance of the unknown resistor is equal to the resistance of a portion of the meter bridge wire between the 0.0cm and the 55.0cm point.
To find the value of the unknown resistor, we can use the principle of the Wheatstone bridge, which states that the ratio of the resistances in the two arms of a balanced bridge is equal.
Let R be the resistance of the unknown resistor, then we have:
R/2.0 = (100 - 55.0)/55.0
Simplifying this expression, we get:
R = 2.0 x (100 - 55.0)/55.0
R = 1.64 ohms
Therefore, the value of the unknown resistor is 1.64 ohms.
Swali 37 Ripoti
Natural radioactivity consists of the emission of
Maelezo ya Majibu
Radioactive decay releases different types of energetic emissions. The three most common types of radioactive emissions are alpha particles, beta particles, and gamma rays.
Swali 38 Ripoti
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?
Maelezo ya Majibu
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.
Swali 39 Ripoti
A car traveled at a uniform speed of 100km/h, spends 15m moving from point A to point B along its route. The distance between A and B is
Maelezo ya Majibu
To calculate the distance between point A and point B, we can use the formula:
Distance = Speed x Time
where the speed is given as 100 km/h and the time is given as 15 minutes, which we need to convert to hours.
1 hour = 60 minutes, so 15 minutes = 15/60 hours = 0.25 hours.
Now, we can substitute these values into the formula:
Distance = 100 km/h x 0.25 h = 25 km
Therefore, the distance between point A and point B is 25 km.
is the correct answer.
Swali 40 Ripoti
The process by which protons are converted into helium atoms with a tremendous release of energy is called?
Maelezo ya Majibu
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.
