WAEC SSCE - Physics - 2010 (Objective)
Pregunta 1 Informe
A nuclide represented as \(^{70}_{32}X\) has a neutron-proton ratio of
Detalles de la respuesta
The neutron-proton ratio of a nuclide is the ratio of the number of neutrons (N) to the number of protons (Z) in its nucleus. For the nuclide \(^{70}_{32}X\), the number 70 represents the total number of nucleons (protons + neutrons) in its nucleus, while 32 represents the number of protons. Therefore, the number of neutrons can be calculated as: N = 70 - 32 = 38 The neutron-proton ratio of this nuclide can then be calculated as: N/Z = 38/32 = 1.19 Therefore, the neutron-proton ratio of this nuclide is approximately 1.2, which corresponds to.
Pregunta 2 Informe
The ability of a wave to spread around corners is called
Detalles de la respuesta
The ability of a wave to spread around corners is called diffraction. When waves encounter an obstacle or an aperture, they bend around the corners or edges of the obstacle or aperture and spread into the region behind the obstacle or aperture. This phenomenon is known as diffraction. The degree of diffraction depends on the size of the obstacle or aperture and the wavelength of the wave. Diffraction is a common phenomenon observed in many types of waves, including sound waves, light waves, and water waves.
Pregunta 3 Informe
a machine is said to be a third class lever when the
Detalles de la respuesta
In a third class lever, the effort is applied between the fulcrum and the load. This means that the effort arm is shorter than the load arm. Examples of third class levers include tweezers and forceps.
Pregunta 4 Informe
a thermometer records 680 mmHg at steam point and 440 mmHg at ice point. The temperature it records at 380 mmHg is
Detalles de la respuesta
To find the temperature at 380 mmHg, we need to interpolate between the steam and ice points. We can use the formula: t = ((P - Pice) / (Psteam - Pice)) x (Tsteam - Tice) + Tice where: - t is the temperature we want to find - P is the pressure we want to use for interpolation (380 mmHg in this case) - Pice is the pressure at the ice point (440 mmHg) - Psteam is the pressure at the steam point (680 mmHg) - Tice is the temperature at the ice point (0oC) - Tsteam is the temperature at the steam point (100oC) Plugging in the values, we get: t = ((380 - 440) / (680 - 440)) x (100 - 0) + 0 t = (-60 / 240) x 100 t = -25oC Therefore, the temperature recorded at 380 mmHg is -25oC.
Pregunta 5 Informe
A solid of mass 0.5kg initially at 50oC melts at 60oC. Calculate the quantity of heat required to melt it completely. [specific heat capacity of the solid =2.0KJ kg-1K-1][Specific latent heat of fusion of solid =1.0 KJ kg-1]
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Pregunta 6 Informe
Which of the following factors does not affect the electric resistance of wire?
Detalles de la respuesta
The factor that does not affect the electric resistance of a wire is mass. Electric resistance is the opposition to the flow of electric current through a conductor. The four factors that affect the resistance of a wire are length, temperature, cross-sectional area, and the type of material used to make the wire. Length: the longer the wire, the higher the resistance as the electric current has to travel further, experiencing more collisions with the wire's atoms and electrons, which leads to a higher resistance. Temperature: an increase in temperature leads to an increase in the wire's resistance. This is because as the temperature increases, the wire's atoms and electrons vibrate more, impeding the flow of current, thus increasing the resistance. Cross-sectional area: the larger the wire's cross-sectional area, the lower its resistance because there are more paths for the electric current to flow through, reducing the chances of collisions with atoms and electrons, thus reducing resistance. Type of material used: different materials have different numbers of free electrons, which affects their resistance. For example, copper has more free electrons than iron, and therefore has a lower resistance. Mass, on the other hand, does not affect the resistance of a wire. The mass of a wire is not related to the number of free electrons or the wire's ability to impede the flow of current.
Pregunta 7 Informe
Which of the following statements best describes a rigid body? A body which
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Pregunta 9 Informe
A lens that is thinner at the middle and thicher at the edges is
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Pregunta 10 Informe
A galvanometer of internal resistance 50\(\Omega\) and full scale deflection of 20 mA is converted into a voltmeter by connecting a resistor of resistance 1950\(\Omega\) in series to it. Calculate the maximum voltage that can be read by the voltmeter
Detalles de la respuesta
The maximum voltage that can be read by the voltmeter can be calculated using the formula: V = I(G + S) Where V is the voltage, I is the current passing through the circuit, G is the galvanometer resistance, and S is the shunt resistance. In this case, the full scale deflection current of the galvanometer is 20 mA, which is 0.02 A. The galvanometer resistance is given as 50 Ω, and the shunt resistance is 1950 Ω. To calculate the current passing through the circuit, we can use Ohm's Law: V = IR Where R is the total resistance in the circuit. In this case, the total resistance is the sum of the galvanometer resistance and the shunt resistance: R = G + S = 50 Ω + 1950 Ω = 2000 Ω Substituting the values into Ohm's Law, we get: V = IR = 0.02 A × 2000 Ω = 40 V Therefore, the maximum voltage that can be read by the voltmeter is 40V. Option D is correct.
Pregunta 11 Informe
The types of motion which a cylindrical drum rolling down an inclined plane undergoes are
Detalles de la respuesta
A cylindrical drum rolling down an inclined plane undergoes rotational and translational motion. Rotational motion refers to the spinning motion around its own axis, which the drum exhibits while rolling down the inclined plane. Translational motion refers to the linear motion of the center of mass of the drum, which moves along the inclined plane. Therefore, the correct answer is "rotational and translational."
Pregunta 12 Informe
The resonant frequency of an a.c circuit is 1000 kHz. If each of the capacitance and inductance in the circuit is reduced by 50%, and no other changes are made, the resonant frequency will become
Detalles de la respuesta
The resonant frequency of an a.c circuit is given by the formula: f = 1/(2π√(LC)) Where f is the resonant frequency, L is the inductance of the circuit, and C is the capacitance of the circuit. If each of the capacitance and inductance in the circuit is reduced by 50%, then the new values of L and C will be 0.5L and 0.5C respectively. Substituting these new values into the formula, we get: f' = 1/(2π√(0.5L * 0.5C)) f' = 1/(2π√(0.25LC)) f' = 1/(0.5π√(LC)) f' = 2f Therefore, the resonant frequency of the circuit will be doubled, which means it will become 2000kHz.
Pregunta 13 Informe
The pressure P, volume V, and absolute temperature T of a given mass of an ideal gas change simultaneously. Which of the followng equations is correct about the gas?
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Pregunta 14 Informe
A moving body of mass 25.0kg undergoes a uniform retardation of 20.0ms-2. Calculate the magnitude of the retardating force
Detalles de la respuesta
The force acting on an object is given by the formula F = ma, where F is the force, m is the mass and a is the acceleration. However, in this case, the object is undergoing retardation, which means its acceleration is negative. Therefore, we have a = -20.0ms-2. The mass of the object is given as 25.0kg. Using the formula F = ma, we can calculate the magnitude of the force as follows: F = m x a = 25.0kg x (-20.0ms-2) = -500N The negative sign indicates that the force is acting in the opposite direction to the motion of the object. However, since the question asks for the magnitude of the force, we take the absolute value, which is 500N. Therefore, the magnitude of the retardating force acting on the object is 500.00N. So, the answer is 500.00N.
Pregunta 15 Informe
Which of the following factors will increase the sensitivity of moving coil meter?
Detalles de la respuesta
A moving coil meter works by measuring the magnetic field produced by an electric current passing through a coil of wire. The sensitivity of the meter refers to how easily it can detect small changes in the current. A strong spring, which opposes the motion of the meter's pointer, will actually decrease the sensitivity of the meter, making it less responsive to small changes in current. A low number of turns on the coil or a small area of the coil will also reduce sensitivity, since there will be less magnetic field produced for a given current. Therefore, the factor that will increase the sensitivity of a moving coil meter is a soft iron core. This is because a soft iron core will amplify the magnetic field produced by the current, making it easier to detect small changes. The iron core will also help to concentrate the magnetic field, further increasing the sensitivity of the meter.
Pregunta 16 Informe
In a thermos flask, heat loss by radiation is minimizes by the
Detalles de la respuesta
In a thermos flask, heat can be transferred by conduction, convection, and radiation. To minimize heat loss by radiation, the inner surface of the outer wall of the flask is usually silvered. This silvered surface is highly reflective and has low emissivity, meaning that it reflects radiation back into the flask and reduces the amount of heat lost to the surroundings. This is the reason why the silvered surface of a thermos flask appears mirror-like. Therefore, the correct answer is "silvered surfaces."
Pregunta 17 Informe
Determine the potential difference. V across the parallel resistors
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Pregunta 18 Informe
Which of the following properties of a long steel bar would alter if the bar were melted, recast into a cube and allowed to cool to its original temperature?
Detalles de la respuesta
The property that would alter if a long steel bar were melted, recast into a cube and allowed to cool to its original temperature is its volume. When the steel bar is melted and recast into a cube, the volume of the cube will be different from the volume of the original steel bar. This is because the shape of the cube is different from that of the bar. However, if the cube is allowed to cool to its original temperature, its volume will be the same as that of the original bar. The other properties such as density, specific heat capacity and electrical resistance will remain unchanged since they are intrinsic properties of the material and do not depend on the shape of the object.
Pregunta 19 Informe
A vertical string, suspended from a fixed point and having a small mass attached to the free end is set into oscillations. Which of the following statements about the system are correct? i. The potential energy of the mass is a minimum at the middle of the swing ii. Its kinetic energy is a maximum at the middle of the swing iii. The sum of the potential and kinetic energies is constant throughout the swing
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Pregunta 20 Informe
A ray of light travels from air to water. The refeactive index of water is given by the expression
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Pregunta 21 Informe
The average speed of an object is determined by dividing the sum of its initial and final speeds by two only when the acceleration is
Detalles de la respuesta
The statement is true only when the acceleration is uniform. Uniform acceleration means that the object is changing its velocity by an equal amount in the same direction during equal intervals of time. In this case, the average speed can be calculated by dividing the sum of initial and final velocity by 2. However, if the acceleration is not uniform, the average speed cannot be calculated using this formula. In that case, we need to use other formulas that take into account the non-uniform acceleration of the object.
Pregunta 22 Informe
Two cars X and Y travelling in opposite directions along the same high way at uniform velocities 110 kmh-1 and 90kmh-1 respectively pass each other at a certain point. The velocity of X relative to Y at the time they pass each other is
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Pregunta 23 Informe
From the diagram, the correct equation for the refractive index n of the medium is
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Pregunta 24 Informe
a body is projected horizonatlly from the top of a cliff 45m above the ground. if the body lands at a distance 30m from the foot of the cliff, calculate the speed of projection. [g = 10ms-2]
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Pregunta 25 Informe
an electron moves with a speed of 2.0 x 106ms-1 in a straight line. Calculate the wave length of the electron wave. [mass of an electron = 9.1 x 10-31 kg][Planck's constant = 6.6 x 10-34Js]
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Pregunta 26 Informe
simple harmonic oscillator has a period of 0.02s and amplitude of 0.25m. Calculate the speed in ms-1 at the centre of the oscillation
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Pregunta 27 Informe
In order to prevent bar magnets from losing their strength, they are stored wih keepers such that the two bars are placed with
Detalles de la respuesta
To prevent bar magnets from losing their strength, they are stored with keepers such that the two bars are placed with unlike poles facing each other and the keepers placed at their ends. This is because the magnetic field of a bar magnet flows from one pole to the other. When two magnets with the same pole are placed together, their magnetic fields interfere with each other and cancel out some of their magnetic properties. On the other hand, when two magnets with opposite poles are placed together, their magnetic fields combine and create a stronger magnetic field. By placing the keepers at the ends, the magnetic field of the bar magnet is confined to the magnet itself and doesn't interact with any external magnetic fields, which could cause it to lose its magnetism over time.
Pregunta 29 Informe
The energy, E stored in an inductor of inductance L when current I passes through it is given by the equation
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Pregunta 30 Informe
Oxidation of the filament in a light bulb is prevented by the introduction of
Detalles de la respuesta
Oxidation is the process of losing electrons, and in a light bulb, the filament gets extremely hot and can react with the oxygen in the air, which can cause the filament to deteriorate and burn out. To prevent this oxidation of the filament, an inert gas is introduced into the bulb, which does not react with the filament even at high temperatures. Of the options given, argon is an inert gas and is commonly used to prevent oxidation of the filament in a light bulb. Therefore, the correct answer is option C - argon.
Pregunta 32 Informe
Which of the following statements about static friction is correct? It
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Pregunta 33 Informe
As the air column of length L in an air pipe decreases, the frequency of the sationary wave emitted
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Pregunta 34 Informe
In the wiring of houses, the fuse is connected to the wire coloured
Detalles de la respuesta
The correct wire color for the fuse in the wiring of houses may vary depending on the country or region. However, in many countries such as the UK and Europe, the wire color for the fuse is brown. This is because brown is the color assigned for live wires in electrical wiring, and the fuse is connected to the live wire for protection against electrical overloading or short-circuiting. Blue is typically used for neutral wires, yellow/green for earth wires, and yellow for the live wire in some countries. It is important to always follow the wiring regulations and guidelines of your region and seek professional assistance if necessary when dealing with electrical wiring.
Pregunta 35 Informe
What is the density of a fuel of relative density 0.72? [Density of water = 1000kg m-3]
Detalles de la respuesta
Relative density, also known as specific gravity, is defined as the ratio of the density of a substance to the density of a reference substance. In this case, the reference substance is water, which has a density of 1000 kg/m3. Therefore, the density of the fuel can be calculated by multiplying the relative density by the density of water: Density of fuel = Relative density x Density of water Density of fuel = 0.72 x 1000 kg/m3 Density of fuel = 720 kg/m3 Hence, the density of the fuel is 720 kg/m3. Therefore, the correct option is: 720 kgm-3
Pregunta 36 Informe
Specific heat capacity 36.4 Jkg-1 K-1 of a body means that when 36.4J of heat energy is supplied to a body of
Detalles de la respuesta
The specific heat capacity of a substance is defined as the amount of heat energy required to raise the temperature of a unit mass of the substance by 1 Kelvin (or 1 degree Celsius). Therefore, if the specific heat capacity of a body is given as 36.4 Jkg\(^{-1}\)K\(^{-1}\), it means that when 36.4 Joules of heat energy is supplied to a body of mass 1kg, the temperature of the body will rise by 1 Kelvin. Therefore, the correct answer is: "mass 1kg, the temperature rises by 1K".
Pregunta 37 Informe
When an object is placed at the principal focus of a concave mirror, the location of the image formed is
Detalles de la respuesta
When an object is placed at the principal focus of a concave mirror, the location of the image formed is at infinity. This is because light rays that are reflected from the mirror are parallel to the principal axis of the mirror, and do not converge or diverge after reflection. Therefore, they appear to be coming from a point at infinity, and the image formed by the mirror appears to be located at this point.
Pregunta 38 Informe
The following devices use plane mirrors in their operations, except
Detalles de la respuesta
The device that does not use plane mirrors in its operation is binoculars. A periscope uses two plane mirrors to reflect light and allow a person to see over an obstacle or around a corner. A sextant uses a plane mirror to reflect the image of the sun or stars onto a scale, enabling sailors to navigate. A kaleidoscope uses multiple plane mirrors to reflect and multiply the image of small colored objects into a visually attractive pattern. However, binoculars use a combination of convex and concave lenses to magnify distant objects, rather than plane mirrors.
Pregunta 39 Informe
Which of the following electromagnetic wave has the longest wavelength?
Detalles de la respuesta
Radio waves have the longest wavelength among the given options. Electromagnetic waves are waves that are created by oscillations in electric and magnetic fields. The wavelength of an electromagnetic wave is the distance between two consecutive peaks or troughs in the wave. The different types of electromagnetic waves have different wavelengths and frequencies, and they are arranged in a spectrum according to their wavelengths. Radio waves have the longest wavelength and the lowest frequency among the electromagnetic waves. They are used for communication, such as in radio and television broadcasting. Gamma rays, on the other hand, have the shortest wavelength and highest frequency among the electromagnetic waves, and are often produced by radioactive decay or nuclear reactions. Infrared and ultraviolet rays have intermediate wavelengths and frequencies between radio waves and gamma rays. Infrared waves are often associated with heat radiation, while ultraviolet rays are known for their ability to cause sunburn and skin damage.
Pregunta 40 Informe
A certain wave has a speed of 20ms-1. If the frequency of the wave is 0.25Hz, calculate the distance between successive crests of the wave
Detalles de la respuesta
The speed of a wave is given by the product of its frequency and wavelength, i.e., speed = frequency x wavelength Rearranging the above equation, we get: wavelength = speed / frequency Substituting the given values, we get: wavelength = 20 / 0.25 = 80m Therefore, the distance between successive crests of the wave is 80m. Answer: 4. 80.0m
Pregunta 41 Informe
A positively charged glass rod is placed near the cap of a positively charged electroscope. The divergence of the leaf is observed to
Detalles de la respuesta
When a positively charged glass rod is brought near the cap of a positively charged electroscope, the charge on the electroscope cap is repelled by the charged glass rod. As a result, the cap loses some of its charge and the electrons move down to the leaves, causing them to acquire a positive charge. The like charges on the leaves cause them to repel each other, causing them to diverge. Therefore, the divergence of the leaf will increase. Thus, the correct option is (b) increase.
Pregunta 42 Informe
Which of the following statements about moving particle is correct?
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Pregunta 44 Informe
Which of the following sources of energy is/are exhausible? i. Solar ii. Fossil fuels iii. Tidal power
Detalles de la respuesta
The term "exhaustible" means that the source of energy is finite and will eventually run out. Solar energy is considered inexhaustible because it comes from the sun and will be available as long as the sun exists. On the other hand, fossil fuels, such as coal, oil, and natural gas, are considered exhaustible because they are finite resources and will eventually be depleted. Tidal power is also considered inexhaustible because it relies on the gravitational pull of the moon and the sun on the Earth's oceans, which will continue as long as the Earth continues to orbit the sun. Therefore, the answer is: ii and iii only.
Pregunta 45 Informe
The amplitude of a sound wave determines its
Detalles de la respuesta
The amplitude of a sound wave determines its loudness. The loudness of a sound is the human perception of its intensity, which is directly related to the amplitude of the sound wave. The larger the amplitude of a sound wave, the louder the sound is perceived to be. However, it is important to note that the pitch, or the perceived highness or lowness of a sound, is determined by the frequency of the sound wave, not its amplitude.
Pregunta 46 Informe
An electric drill rated 400W is used to drill a hole in copper of mass 400g in 20s. Calculate the rise in temperature if all the heat produced is absorbed by the copper. [specific heat capacity of copper = 400Jkg-1K-1]
Detalles de la respuesta
To calculate the rise in temperature of the copper, we need to use the formula: heat energy = mass x specific heat capacity x temperature change We know the power of the drill (400W) and the time taken (20s), so we can calculate the total energy produced: total energy = power x time total energy = 400W x 20s total energy = 8000J We also know the mass of the copper (400g) and the specific heat capacity of copper (400Jkg-1K-1). To calculate the temperature change, we rearrange the formula: temperature change = heat energy / (mass x specific heat capacity) temperature change = 8000J / (0.4kg x 400Jkg-1K-1) temperature change = 50K Therefore, the rise in temperature of the copper is 50oC. So the correct option is: 50oC.
Pregunta 47 Informe
Which of the following instruments is best for measuring the diameter of a thin constantan wire?
Detalles de la respuesta
The micrometer screw gauge is the best instrument for measuring the diameter of a thin constantan wire. Micrometers are highly sensitive instruments that can measure small distances accurately. They are commonly used in precision engineering to measure the thickness of wires and the diameter of cylinders. The micrometer screw gauge has a spindle that moves as a thimble is turned, and the distance moved is indicated on a graduated scale. This allows for very precise measurements of small distances, such as the diameter of a thin wire. Callipers, metre rule, and vernier callipers are useful for measuring larger distances but are not as accurate as a micrometer screw gauge for measuring small distances.
Pregunta 48 Informe
In a cathode ray tube, the function of the x-plates is to
Detalles de la respuesta
In a cathode ray tube, the x-plates are used to deflect the electron beam horizontally. The electron beam is generated by the cathode and accelerated by the anode towards the screen. The y-plates are used to deflect the beam vertically. By applying appropriate voltages to the x-plates and y-plates, the electron beam can be made to scan across the screen and form a visible image. Therefore, option A, which states that the x-plates deflect the electron beam horizontally, is the correct answer.
Pregunta 49 Informe
The advantages of the thermoelectric thermometer include the following characteristics except that it
Detalles de la respuesta
The thermoelectric thermometer is a type of temperature measuring device that utilizes the Seebeck effect to measure temperature. It consists of two different metals or semiconductors connected together, which generate a small voltage when there is a temperature difference between the two junctions. This voltage is directly proportional to the temperature difference between the two junctions, making it an effective and reliable way of measuring temperature. The advantages of the thermoelectric thermometer include its ability to measure rapidly changing temperatures, measure high and low temperatures, and measure temperature almost at a point. Additionally, it is fairly sensitive, which allows it to detect even small changes in temperature. Therefore, the statement that is not true is that the thermoelectric thermometer is not fairly sensitive.
Pregunta 50 Informe
Neutrons are used to induce artificial radioactivity because they
Detalles de la respuesta
Neutrons are used to induce artificial radioactivity because they have no charge and can penetrate atomic nuclei, unlike positively charged alpha particles or negatively charged beta particles. When neutrons are absorbed by the nucleus of an atom, they can cause the nucleus to become unstable and undergo radioactive decay. This can result in the emission of various forms of radiation, such as alpha particles, beta particles, or gamma rays, depending on the type of decay that occurs. Therefore, neutrons can be used to induce artificial radioactivity in a target material, which can then be used for various purposes such as medical imaging, cancer treatment, and nuclear power generation.
