WAEC SSCE - Physics - 2009 (Objective)

Question 1 Report

In which of the following states of matter do the molecules vibrate about their mean positions?

liquids only

solids only Correct answer

liquids and gasses only

solids, liquids and gases

Answer Details

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Quantity Of Heat

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Question 2 Report

Which of the following properties of a steel bar can be measured in terms of the dimension of length only?

weight

density

pressure

volume Correct answer

Answer Details

Read lesson note on Position, Distance And Displacement (WAEC)

Position, Distance And Displacement

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Question 3 Report

An electron of mass 9.1 x 10^-31 kg moves with a speed of 10⁷ms^-1. Calculate the wavelength of the associates wave[h = 6.6 x 10^-34Js]

9.0 x 10^-24m

4.55 x 10^-17m

7.25 x 10^-11m Correct answer

6.20 x 10^-8m

Answer Details

The wavelength of the associated wave of a moving particle can be determined using the de Broglie equation, which relates the particle's momentum to its wavelength: λ = h / p where λ is the wavelength, h is Planck's constant, and p is the momentum of the particle. We can determine the momentum of the electron using the formula: p = m * v where p is the momentum, m is the mass, and v is the velocity. Substituting the given values, we get: p = (9.1 x 10^-31 kg) * (10^7 ms^-1) = 9.1 x 10^-24 kgms^-1 Substituting p into the de Broglie equation, we get: λ = h / p = (6.6 x 10^-34 Js) / (9.1 x 10^-24 kgms^-1) = 7.25 x 10^-11 m Therefore, the wavelength of the associated wave is 7.25 x 10^-11 m. The correct option is (c) 7.25 x 10^-11 m.

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Thermal Expansion

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Question 4 Report

A resistor of resistance R is connected to a battery of negligible internal resistance. If a siilar resistor is connected in series with it the

effective resistance of the circuit is halved

total power dissipated is doubled Correct answer

total current in the circuit is halved

terminal voltage is halved

Answer Details

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Simple A.C Circuits

Electrostatics

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Question 5 Report

A satellite in circular motion around the earth does not have

a gravitational force acting on it

a uniform velocity Correct answer

an acceleration

a centripetal force acting on it

Answer Details

A satellite in circular motion around the earth does not have a uniform velocity. Even though its speed is constant, the direction of its velocity is constantly changing due to the centripetal force provided by the gravitational force of the earth. Therefore, it has an acceleration towards the center of the circle, which is equal in magnitude to the centripetal force acting on it.

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Gravitational Field

Equilibrium Of Forces

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Question 6 Report

Which of the following characteristics of light determines its colour?

velocity

wavelength Correct answer

amplitude

intensity

Answer Details

The characteristic of light that determines its color is wavelength. Wavelength is the distance between consecutive peaks or troughs of a wave. Different colors of light have different wavelengths, with longer wavelengths corresponding to colors like red and orange, and shorter wavelengths corresponding to colors like blue and violet. So, when light interacts with an object and some wavelengths are absorbed while others are reflected or transmitted, the color that we perceive is determined by the wavelengths that are reflected or transmitted to our eyes. Therefore, the wavelength is responsible for the color of light we see.

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Light Energy

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Question 7 Report

If the direction of the curent in a straight wire is reversed, the magnetic field

remains the same

becomes parallel to the wire

ceases to exist

is oppositely directed Correct answer

Answer Details

When an electric current flows through a straight wire, it generates a magnetic field around the wire. The direction of the magnetic field is dependent on the direction of the current flow. If the direction of the current flow is reversed, then the direction of the magnetic field will also be reversed. Therefore, the correct answer is: the magnetic field is oppositely directed.

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Electric Field

Electromagnetic Field (Part 2)

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Question 8 Report

An isolated metal sphere of radius R, carrying an electric charge Q, is situated in the medium of relative permitivity, E_r. A test charge is placed at a point p, distance r from the surface of the sphere. Let E_o represent the permitivity of free space. The magnitude of the electric field intensity at P is given by the expression

\(\frac{Q}{4 \pi E_o E_r r^2}\)

\(\frac{Q}{4 \pi E_o E_r(R + r)^2}\)

\(\frac{Q}{4 \pi E_o E_r(R - r)^2}\)

\(\frac{Q}{4 \pi E_o E_rR^2}\) Correct answer

Answer Details

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Electrostatics

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Question 9 Report

Which of the following is not a part of the electro-magnetic spectrum?

x-rays

microwaves

infrared radiation

alpha rays Correct answer

Answer Details

Alpha rays are not part of the electromagnetic spectrum. The electromagnetic spectrum includes all forms of electromagnetic radiation that differ in wavelength and frequency, including radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays. Alpha rays are actually alpha particles, which consist of two protons and two neutrons and are emitted by some types of radioactive materials. Alpha particles have a positive charge and are relatively large compared to other types of radiation, so they are not part of the electromagnetic spectrum.

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Description Property Of Fields

Sound Waves

Electromagnetic Waves: Types Of Radiation In Electromagnetic Spectrum

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Question 10 Report

Sound interference is necessary to produce the phenomenon of

beats Correct answer

doppler effect

acoustic resonance

echo

Answer Details

Sound interference is necessary to produce the phenomenon of beats. Beats are produced when two sound waves of slightly different frequencies are superimposed on each other. The interference of these sound waves causes the sound intensity to oscillate, resulting in a periodic variation of loudness known as beats. These beats can be heard as a throbbing sound. The number of beats produced per second is equal to the difference in frequency between the two sound waves. The phenomenon of beats is used in tuning musical instruments to ensure they are in tune with each other.

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Question 11 Report

When a conductor mounted on an insulating stand is charged and left for sometime, the conductor eventually loses all its charges. This is because the

electric charges evaporate from the surface of the conductor

charges are connected to earth

charges on the conductor are neutralized by opposite charges from the surrounding air Correct answer

charges ionize the surrounding air

Answer Details

When a conductor mounted on an insulating stand is charged and left for some time, the conductor eventually loses all its charges. This happens because the charges on the conductor attract opposite charges from the surrounding air, which neutralize the charge on the conductor. This process is called electrostatic discharge or simply discharge. As a result, the charges are dissipated, and the conductor becomes neutral again. Therefore, the correct option is "charges on the conductor are neutralized by opposite charges from the surrounding air".

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Electrostatics

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Question 12 Report

A concave mirror forms a magnified and errect image only when the object is placed

at the centre of curvature

at the focus

between the focus and the pole of the mirror Correct answer

beyound the radius of curvature

Answer Details

A concave mirror forms an image of an object when light rays from the object are reflected off the mirror. The image formed can either be magnified or reduced in size, and it can be erect or inverted depending on where the object is placed in relation to the mirror. In this question, we are told that the concave mirror forms a magnified and erect image. For this to happen, the object must be placed between the focus and the pole of the mirror. This is because, in a concave mirror, light rays coming parallel to the principal axis are reflected and converge at the focus. When an object is placed between the focus and the pole of the mirror, the reflected rays will still converge and form a real image that is magnified and erect. If the object is placed at the focus, the reflected rays will be parallel, and no image will be formed. If the object is placed beyond the radius of curvature, the image formed will be real, but it will be inverted. If the object is placed at the center of curvature, the image formed will be real, inverted, and the same size as the object.

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Properties Of Waves: Reflection, Refraction, Diffraction

Electrostatics

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Question 13 Report

The period of a simple pendulum of length 80.0cm was found to have doubled when the length of the pendulum was increased by X. Calculate X.

26.7cm

40.0cm

160.0cm

240.0cm Correct answer

Answer Details

The period of a simple pendulum depends on its length. The relationship between the period (T) of a simple pendulum and its length (L) is given by the formula: T = 2π√(L/g), where g is the acceleration due to gravity. If the period of the pendulum doubles, then the new period (T') is twice the original period (T): T' = 2T = 4π√(L/g). If the length of the pendulum is increased by X, then the new length (L') is: L' = L + X. Substituting this into the formula for the new period gives: T' = 2π√((L+X)/g) Since T' = 2T, we can equate the two expressions for T' and simplify: 4π√(L/g) = 2π√((L+X)/g) Squaring both sides and canceling the common factor of 4π²/g, we get: L = (L+X)/2 Solving for X gives: X = L Therefore, the length of the pendulum needs to be increased by 80.0 cm to double its period, so X = 80.0 cm. The answer is option D: 240.0 cm.

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Simple Harmonic Motion

Work, Energy And Power

Measurements And Units

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Question 14 Report

The maximum displacement of a vibrating tunning fork is its

amplitude Correct answer

frequency

period

wavelength

Answer Details

The maximum displacement of a vibrating tuning fork is its amplitude. In a vibrating system, amplitude refers to the maximum displacement of the vibrating object from its equilibrium or rest position. For a tuning fork, the amplitude refers to the maximum distance that the prongs of the fork move away from their resting position when they are vibrating. The amplitude of a tuning fork determines the intensity or loudness of the sound it produces. A larger amplitude produces a louder sound, while a smaller amplitude produces a softer sound. Therefore, the correct option is "amplitude".

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Scalars And Vectors

Equilibrium Of Forces

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Question 15 Report

An isolated metal sphere of radius R, carrying an electric charge Q, is situated in the medium of relative permitivity, E^r. A test charge is placed at a point p, distance r from the surface of the sphere. Let E^o represent the permitivity of free space. The electric potential at p is given by the expression

\(\frac{Q}{4 \pi E_o E_r}\)

\(\frac{Q}{4 \pi E_o E_r (R +r)}\)

\(\frac{Q}{4 \pi E_o E_r(R - r)}\)

\(\frac{Q}{4 \pi E_o E_rR}\) Correct answer

Answer Details

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Electric Field

Electromagnetic Field (Part 2)

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Question 16 Report

A body moving in a circle at constant speed has i. a velocity tangent to the circle ii. a constant kinetic energy ii. an acceleration directed towards the circmference of the circle ii. an acceleration directed towards the circumference of the circle. Which of the statements above are correct?

i and ii only Correct answer

ii and iii

ii and iii only

i and iii only

Answer Details

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Scalars And Vectors

Motion

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Question 17 Report

A body of volume 0.046m³ is immersed in a liquid of density 980kgm^-3 with \(\frac{3}{4}\) of its volume submerged. Calculate the upthrust on the body. [g = 10ms^-2]

11.27N

33.81N

112.70N

338.10N Correct answer

Answer Details

When an object is immersed in a fluid, it experiences an upward force called buoyant force or upthrust. This force is equal to the weight of the fluid displaced by the object. In this case, the volume of the object submerged in the fluid is \(\frac{3}{4}\) of its total volume. So, the volume of fluid displaced by the object is \(\frac{3}{4}\) x 0.046m³ = 0.0345m³ The weight of this displaced fluid can be calculated as: mass = density x volume = 980kgm^-3 x 0.0345m³ = 33.81kg weight = mass x g = 33.81kg x 10ms^-2 = 338.1N Therefore, the upthrust on the body is 338.1N. So, the correct answer is (C) 338.10N.

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Pressure

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Question 18 Report

A rod of initial lenght 2m at a temperature of 25^oC is heated to 80^oC. Calculate the increase in length of the rod if its linear expansivity is 4.0 x 10^-3K^-1

0.26m

0.44m Correct answer

0.53m

0.84m

Answer Details

The increase in length of the rod can be calculated using the formula: ΔL = αLΔT where: ΔL = change in length α = linear expansivity coefficient L = initial length ΔT = change in temperature Substituting the given values, we have: ΔL = (4.0 x 10^-3 K^-1) x (2m) x (80°C - 25°C) ΔL = 0.44m Therefore, the increase in length of the rod is 0.44m. Note: When a material is heated, its length increases due to the expansion of its particles. The linear expansivity coefficient (α) represents the fractional change in length per unit change in temperature.

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Temperature And Its Measurement

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Question 19 Report

Two forces 6N and 8N, act eastwards and northwards respectively on a body. Calculate the magnitude of their equilibrant

10N Correct answer

14N

Answer Details

When two forces act on a body, their resultant force can be calculated using vector addition. The equilibrant is the force required to balance the two forces and bring the body into a state of equilibrium. It has the same magnitude as the resultant force but acts in the opposite direction. To calculate the equilibrant, we need to find the resultant force of the two given forces. We can do this by drawing a vector diagram or using trigonometry. Using trigonometry, we can find the magnitude of the resultant force as follows: \begin{align*} F_{\text{resultant}} &= \sqrt{(6\text{N})^2 + (8\text{N})^2} \\ &= \sqrt{36\text{N}^2 + 64\text{N}^2} \\ &= \sqrt{100\text{N}^2} \\ &= 10\text{N} \end{align*} The equilibrant has the same magnitude as the resultant force but acts in the opposite direction. Therefore, the magnitude of the equilibrant is also 10N. So, the correct answer is 10N.

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Equilibrium Of Forces

Measurements And Units

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Question 20 Report

The angle of incidence of a ray of light on a plane mirror is 55^o. Determine the angle between the reflected ray and the mirror

35^o Correct answer

45^o

55^o

110^o

Answer Details

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Reflection Of Light At Plane And Curved Surfaces

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Question 21 Report

Which of the following waves is not transverse

light waves

sound waves Correct answer

sea waves

radio waves

Answer Details

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Question 22 Report

A machine of efficiency 80% is used to lift a box. If the effort applied by the machine is twice the weight of the box. Calculate the velocity ratio of the machine

0.50

0.63 Correct answer

0.80

1.60

Answer Details

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Work, Energy And Power

Simple Machines

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Question 23 Report

A wire of resistivity 4.40 x 10^-5\(\Omega\) cm has a cross sectional area of 7.50 x 10^-4 cm². Calculate the length of the wire that will be required to make a 4.0\(\Omega\) resistor

82.50 cm

68.18cm Correct answer

15.90cm

11.95cm

Answer Details

The resistance of a wire can be calculated using the formula R = \(\frac{\rho L}{A}\), where R is the resistance, \(\rho\) is the resistivity of the wire, L is the length of the wire, and A is the cross-sectional area of the wire. In this problem, we are given the resistivity of the wire and the cross-sectional area of the wire. We are also told that the wire needs to have a resistance of 4.0\(\Omega\). We can rearrange the formula to solve for L: L = \(\frac{AR}{\rho}\) Substituting the values given in the question, we have: L = \(\frac{(7.50 \times 10^{-4} cm^{2}) (4.0 \Omega)}{4.40 \times 10^{-5} \Omega cm}\) = 68.18 cm Therefore, the length of the wire required to make a 4.0\(\Omega\) resistor is 68.18 cm. The correct option is: 68.18cm.

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Electrostatics

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Question 24 Report

The following properties of a solid are measured on earth i. weight ii. specific heat capacity iii. density. Which of the properties will hav a different value if measured in space?

i only Correct answer

ii only

iii only

ii and iii only

Answer Details

The property that will have a different value if measured in space is (i) weight. Weight is the force with which an object is attracted towards the center of the earth due to gravity. In space, there is no gravity or the gravitational force is very weak compared to that on earth. Therefore, the weight of an object measured on earth will be different from the weight of the same object measured in space. On the other hand, specific heat capacity and density are intrinsic properties of a substance that do not depend on the gravitational force, so they will have the same value whether measured on earth or in space. Thus, the answer is (i) only.

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Question 25 Report

as a bicycle Tyre was being pumped up, it was noticed that contrary to Boyle's law the volume increased as the pressure increased. The best explanation of this is that Boyle's law is only true for

ideal gases Correct answer

a fixed mass of gas

a mixture of gases

a gas at variable temperature

Answer Details

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Gas Laws

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Question 26 Report

Which of the following types of types of motion will be produced when a pair of equal and opposite non-collinear parallel forces acts on a body?

vibrational motion

random motion

translational motion

rotational motion Correct answer

Answer Details

When a pair of equal and opposite non-collinear parallel forces act on a body, a rotational motion will be produced. This is because the two forces will cause a torque or moment about the center of mass of the body, which will result in the body rotating around that point. The magnitude of the torque is proportional to the product of the forces and the perpendicular distance between them, which is also known as the lever arm. Therefore, the greater the force or the longer the lever arm, the greater the torque and the faster the body will rotate. The other options, such as vibrational motion, random motion, and translational motion, do not apply in this scenario because the forces are not acting in such a way as to cause those types of motion.

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Question 27 Report

In a hydraulic press, a force of 40N is applied to the smaller priston of area 10cm². If the area of the larger piston is 200cm², calculate the force obtained

800N Correct answer

500N

80N`

50N

Answer Details

In a hydraulic press, the pressure exerted is constant throughout the system. The pressure exerted is given by the formula: Pressure = Force / Area The force is directly proportional to the product of the pressure and area. F ∝ P.A If F₁ is the force applied on the smaller piston of area A₁, and F₂ is the force on the larger piston of area A₂, then: F₁ / A₁ = F₂ / A₂ Rearranging the formula above to solve for F₂: F₂ = F₁ x (A₂ / A₁) Substituting the values given in the question, we get: F₂ = 40N x (200cm² / 10cm²) = 800N Therefore, the force obtained is 800N. The answer is (a) 800N.

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Friction

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Question 28 Report

It takes 4 minutes to boil a quantity of water using an electrical heating coil. How long will it take to boil the same quantity of water using the same coil if the current is doubled? [Neglect any external heat losses]

8 minutes

4 minutes

2 minutes Correct answer

1 minute

Answer Details

If the current is doubled, the heating power will also double, which means that the coil will generate twice as much heat per unit of time. Since the amount of water to be boiled is the same, the amount of heat needed to raise its temperature to boiling point will also be the same. However, with twice the heating power, the time required to deliver that amount of heat will be halved. Therefore, the time it will take to boil the water using the doubled current will be half of the time it took with the original current, which is 2 minutes. So the answer is 2 minutes.

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Question 29 Report

Two isotopes of uranium are designed as \(^{238}U\) and \(^{235}U\). The numbers 238 and 235 represent their

atomic numbers

nucleon numbers Correct answer

proton numbers

neutron numbers

Answer Details

The numbers 238 and 235 represent the nucleon numbers of the two isotopes of uranium, namely \(^{238}U\) and \(^{235}U\). The nucleon number represents the total number of protons and neutrons in the nucleus of an atom. Therefore, \(^{238}U\) has a nucleus consisting of 238 protons and neutrons, and \(^{235}U\) has a nucleus consisting of 235 protons and neutrons. Atomic number, on the other hand, represents the number of protons in the nucleus of an atom, and proton number and neutron number are not commonly used scientific terms.

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Structure Of The Atom (Nigeria Only)

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Question 30 Report

A faulty thermometer registers 102.5^oC t 100^oC. If the thermometer has no zero hour, what will it register at 55^oC?

54.6^oC

55.0^oC

56.0^oC

56.4^oC Correct answer

Answer Details

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Temperature And Its Measurement

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Question 31 Report

A moving body accelerates when it

changes its direction at constant speed

mauntains a constant linear speed

covers equal distances in equal times in a straight line Correct answer

is acted upon by balanced forces

Answer Details

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Newton’s Laws Of Motion

Gravitational Field

Speed And Velocity

Equilibrium Of Forces

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Question 32 Report

A stone of mass 0.5kg is dropped from a height of 12m. Calculate its maximum kinetic energy. [g = 10ms^-1]

3.0J

6.0J

30.0j

60.0J Correct answer

Answer Details

When the stone is dropped, it gains potential energy due to its position above the ground. This potential energy is converted into kinetic energy as the stone falls towards the ground. The maximum kinetic energy of the stone will occur just before it hits the ground when all its potential energy has been converted to kinetic energy. The potential energy of the stone is given by the formula P.E. = mgh, where m is the mass of the stone, g is the acceleration due to gravity and h is the height from which it is dropped. Substituting the given values into the formula, we get: P.E. = (0.5 kg)(10 ms^-2)(12 m) = 60 J Since the maximum kinetic energy is equal to the potential energy at the maximum height, the maximum kinetic energy of the stone is also 60 J. Therefore, the correct option is (d) 60.0 J.

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Friction

Work, Energy And Power

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Question 33 Report

Light travelling through a small pinhole usually does not make a shadow with a distinct sharp edge because of

diffraction Correct answer

inteference

reflection

refraction

Answer Details

The phenomenon that causes light travelling through a small pinhole to not make a shadow with a distinct sharp edge is called diffraction. Diffraction is the bending of waves around an obstacle or through an opening. When light waves pass through a small pinhole, they bend and spread out after passing through the hole. As a result, the edges of the shadow become blurred, and a distinct sharp edge cannot be seen. This effect is also observed when sound waves pass through small openings, such as in the case of musical instruments. Therefore, the correct option is "diffraction".

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Properties Of Waves: Reflection, Refraction, Diffraction

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Question 34 Report

Which of the following is used to measure relative humidity?

hydrometer

barometer

hypsometer

hygrometer Correct answer

Answer Details

The instrument used to measure relative humidity is called a hygrometer. A hygrometer is a device that measures the amount of water vapor in the air or the humidity level. It measures the amount of moisture in the air by using two thermometers. One of the thermometers is dry while the other is kept wet. The difference in temperature between the two thermometers is then measured, and this difference is used to calculate the relative humidity of the air. Therefore, the correct option is (d) hygrometer.

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Pressure

Measurements And Units

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Question 35 Report

A battery of e.m.f. 12.0V and internal resistance0.5\(\Omega\) is connected to 1.5\(\Omega\) and 4.0\(\Omega\) series resistor. Calculate the terminal voltage of the battery.

13.0V

11.0V Correct answer

3.0V

1.0V

Answer Details

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Capacitors

Current Electricity

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Question 36 Report

An inductor of inductance 1.0H is connected in series with a capacitor of capacitance 2.0\(\mu F\) in an a.c. circuit. to resonate

112.5Hz Correct answer

225.0Hz

323.5Hz

707.1Hz

Answer Details

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Capacitors

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Question 37 Report

A thin lens is placed 50cm from an illustrated object. The image produced has linear magnification of \(\frac{1}{4}\). Calculate the power of the lens in dioptres

2.5D

5.0D

10.0D Correct answer

25.0D

Answer Details

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Electrostatics

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Question 38 Report

Electric energy is measured in

ampere

coulomb

kilowatt-hour Correct answer

kilowatt

Answer Details

Electric energy is measured in kilowatt-hour (kWh). A kilowatt-hour is a unit of energy equivalent to the energy used by a load of one kilowatt in one hour. This unit is commonly used by electric utility companies to measure the amount of energy consumed by households or businesses. An ampere is a unit of electric current, while a coulomb is a unit of electric charge. A kilowatt is a unit of power, which is the rate at which energy is consumed or produced. Therefore, none of these units are suitable for measuring electric energy.

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Electrical Energy And Power

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Question 39 Report

The main difference between between x-rays and \(\gamma-rays\) lies in their

ionizing ability

absorption rate

mode of production

mode of propagation Correct answer

Answer Details

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Electromagnetic Waves: Types Of Radiation In Electromagnetic Spectrum

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Question 40 Report

An ammeter connected to an a.c circuit records 5.5. The peak current in the circuit is

7.8A Correct answer

7.1A

3.8A

3.5A

Answer Details

In an AC circuit, the current is constantly changing direction and amplitude, and we use the root mean square (rms) value to measure the effective current flowing in the circuit. The peak value is the maximum value the current can reach, and it is equal to the square root of 2 times the rms value. So, in this case, we can use the formula: Peak value = sqrt(2) x rms value Given that the ammeter records 5.5, which is the rms value, we can calculate the peak value as follows: Peak value = sqrt(2) x 5.5 Peak value = 7.77 Rounded to one decimal place, the answer is 7.8A. Therefore, option A is the correct answer.

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Question 41 Report

A body of mass 5kg movimg with a velocity of 30ms^-1 due east is suddenly hit by another body and changes its velocity to 50ms^-1 in the same direction. Calculate the magnitude of the impulse received.

100Ns Correct answer

150Ns

250Ns

400Ns

Answer Details

To calculate the magnitude of the impulse received by the body, we need to use the impulse-momentum theorem, which states that the impulse applied to a body is equal to the change in momentum of the body. The momentum of an object is defined as the product of its mass and velocity, i.e., P = mv, where P is momentum, m is mass, and v is velocity. The change in momentum (ΔP) of the body can be calculated as the difference between the final momentum (P_f) and the initial momentum (P_i), i.e., ΔP = P_f - P_i. In this case, the initial momentum of the body is given by P_i = mv = 5 kg x 30 m/s = 150 kg m/s (due east), and the final momentum is given by P_f = mv = 5 kg x 50 m/s = 250 kg m/s (due east). Therefore, the change in momentum (ΔP) of the body is: ΔP = P_f - P_i = 250 kg m/s - 150 kg m/s = 100 kg m/s (due east). The magnitude of the impulse (J) received by the body is equal to the change in momentum (ΔP), i.e., J = ΔP = 100 kg m/s. Therefore, the answer is option A: 100 Ns.

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Motion

Work, Energy And Power

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Question 42 Report

A cell of e.m.f. 1.5V is connected in series with a resistor of resistance 3.0\(\Omega\). A voltmeter connected across the cell registers 0.9V. Calculate the internal resistance of the cell

2.0\(\Omega\). Correct answer

3.0\(\Omega\).

5.0\(\Omega\).

6.0\(\Omega\).

Answer Details

The internal resistance of a cell can be calculated using the equation: r = (E - V)/I where r is the internal resistance of the cell, E is the e.m.f. of the cell, V is the voltage across the cell, and I is the current passing through the circuit. In this case, the e.m.f. of the cell is given as 1.5V, and the resistance of the resistor is 3.0\(\Omega\). Since the cell and the resistor are connected in series, the current passing through them will be the same. We can calculate the current using Ohm's law: I = V/R = 0.9V/3.0\(\Omega\) = 0.3A Now we can use the formula for the internal resistance: r = (E - V)/I = (1.5V - 0.9V)/0.3A = 2.0\(\Omega\) Therefore, the internal resistance of the cell is 2.0\(\Omega\). Answer option A is correct.

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Electric Cells

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Question 43 Report

A boat is rocked by waves of speed 30ms^-1 whose successive crest are 10m apart. Calculate the rate at which the boat recieves the waves

30s^-1

10s^-1

3s^-1 Correct answer

1s^-1

Answer Details

The rate at which the boat receives the waves is equal to the frequency of the waves. The distance between successive crests of the waves is 10m, which is also the wavelength of the wave. Therefore, the formula for the speed of the wave can be written as: speed = wavelength x frequency We are given the speed of the wave as 30m/s and the wavelength as 10m. Rearranging the formula above to solve for frequency gives: frequency = speed / wavelength Substituting the values we have: frequency = 30m/s / 10m = 3s^-1 Therefore, the rate at which the boat receives the waves is 3s^-1, which is option (C).

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Production And Propagation Of Waves

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Question 44 Report

Which of the following factors affect the rate of evaporation of a liquid? i. Exposed surface area ii Temperature of the surroundings iii. Thermal capacity of the liquid iv. Relative humidity of the surroundings

ii and iii only

ii, iii and iv only

i, iii and iv only

i, ii amd iv only Correct answer

Answer Details

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Heat Energy

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Question 45 Report

When table salt is added to ice, the melting point of the ice

is raised

is lowered Correct answer

remains unchanged

is first raised, then lowered

Answer Details

When table salt (sodium chloride) is added to ice, it lowers the melting point of the ice. This is because salt dissolves in the thin layer of water on the surface of the ice, forming a saltwater solution. The saltwater solution has a lower freezing point than pure water, so it requires a lower temperature to freeze. As a result, the ice melts at a lower temperature when salt is added, leading to a lowering of the melting point. This phenomenon is called freezing point depression.

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Temperature And Its Measurement

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