Physics 2023

Objective Questions

The instrument used to measure relative humidity is a

A) Barometer B) Hydrometer C) Hygrometer D) Mamometer

Correct Answer: C) Hygrometer

Which part of the human eye performs the same function as the diaphragm in a lens camera?

A) Choroid B) Iris C) Cornea D) Retina

Correct Answer: B) Iris

An electron moves from an energy level of -8.6 eV to another level of -3.5 eV. Determine the frequency of the absorbed radiation.
[1 eV = 1.6 × 10⁻¹⁹ J, h = 6.6 × 10⁻³⁴ Js]

A) 2.93×10¹⁵ Hz B) 3.59×10¹⁶ Hz C) 5.39×10¹⁵ Hz D) 1.24×10¹⁵ Hz

Correct Answer: A) 2.93×10¹⁵ Hz

A ball of mass 0.8 kg is dropped from a height, H. Just before hitting the ground, its velocity is 5.0 m/s. Determine H. [g = 10 m/s²]

A) 1.25 m B) 4.00 m C) 6.25 m D) 1.60 m

Correct Answer: A) 1.25 m

Which of the following statements about latent heat are correct?

I. When ice melts, latent heat is absorbed
II. When water freezes, latent heat is given off
III. When water evaporates, latent heat is absorbed
IV. When water vapour condenses, latent heat is absorbed

A) I and IV only B) II and III only C) I, II and III only D) II, III and IV only

Correct Answer: C) I, II and III only

Increasing the frequency of a sound wave produces a sound with

A) Longer wavelength B) Reduced loudness C) Higher pitch D) More overtones

Correct Answer: C) Higher pitch

Which of the following diagrams correctly illustrates the mode of oscillation of air in a tube for the first overtone?

A) A B) B C) C D) D

Correct Answer: B) B

In a mass spectrometer, an ion of charge, q, and mass, m, moving in a path of radius, r, in a field of flux density, B, has a speed of

A) mr/qB B) mq/qr C) Bqr/m D) mq/Br

Correct Answer: C) Bqr/m

A sound of frequency 512 Hz reaches a listener 100 m away. If the sound travels in air at s.t.p., what is its wavelength?
[Speed of sound in air = 331 m/s]

A) 1.550 m B) 0.646 m C) 5.120 m D) 0.195 m

Correct Answer: B) 0.646 m

In the Rutherford scattering experiment, a beam of alpha particles was fired at a thin gold film and few of the particles were deflected considerably. This shows that the nucleus of an atom

A) Contains protons and electrons distributed in a tiny volume B) Is positively charged and is concentrated in a tiny volume C) Is distributed in a tiny volume and emits alpha particles D) Is concentrated in a tiny volume and contains alpha particles

Correct Answer: B) Is positively charged and is concentrated in a tiny volume

A charge of 10 C is transferred across a potential difference of 220 V. Determine the work done.

A) 22 J B) 2200 J C) 210 J D) 230 J

Correct Answer: B) 2200 J

A solenoid is constructed by winding an insulated copper on a long test tube. A constant direct current is passed through the solenoid. Which of the following actions will not increase the strength of the magnetic field of the solenoid? Inserting a

A) Nickel rod in the test tube B) Brass rod in the test tube C) Soft iron rod in the test tube D) Steel rod in the test tube

Correct Answer: B) Brass rod in the test tube

The following statements are advantages of a solid dielectric material between the plates of a capacitor except that

A) It keeps the plates at a fixed separation B) The maximum potential difference the capacitor can withstand is increased C) The capacitance of the capacitor of given dimensions is much greater than that of the plates in a vacuum D) It increases the electrical conduction of the capacitor

Correct Answer: D) It increases the electrical conduction of the capacitor

Which of the following statements about a ferromagnetic material is correct?

A) It attracts non magnetic materials B) Has low relative permeability C) Repels other magnetic materials D) Has a high susceptibility

Correct Answer: D) Has a high susceptibility

A ball P is released from the roof of a building at the same time as another ball, Q, is thrown vertically upward from the base of the building. Which of the following statements is correct?

A) The acceleration of P is greater than that of Q and both are in the same direction B) The acceleration of P is equal to that of Q and both are in the same direction C) The acceleration of P is equal to that of Q and are in opposite directions D) The acceleration of P is less than that of Q and both are in the same directions

Correct Answer: C) The acceleration of P is equal to that of Q and are in opposite directions

A planet has mass, M, and radius R. If the universal gravitational constant is G, what is the expression for the escape velocity of an object on the planet?

A) GR√2 B) 2GM√R C) 2G√R D) GM√R

Correct Answer: B) 2GM√R

The specific latent heat of vaporization of lead is 8.7 × 10⁵ J/kg. This means that 8.7 × 10⁵ J of thermal energy is required to change:

A) A given mass of molten lead to vapour at constant temperature and pressure B) 1 kg of molten lead to vapour at constant temperature and pressure C) 1 kg of solid lead to vapour at constant temperature and pressure D) 1 kg of molten lead to vapour for every degree rise in temperature

Correct Answer: B) 1 kg of molten lead to vapour at constant temperature and pressure

A 100 kg device is pulled up a plane inclined at 30° to the horizontal with a force of 1000 N. If the coefficient of friction between the device and the surface is 0.25, determine the total force opposing the motion. [g = 10 m/s²]

A) 283.5 N B) 975.0 N C) 216.5 N D) 716.5 N

Correct Answer: C) 216.5 N

Two objects, A and B, accelerate from rest at uniform rates. B accelerates twice as much as A. Compared to A, B travels:

A) Two times as far B) Three times as far C) Six times as far D) At the same distance as

Correct Answer: A) Two times as far

The diagram below illustrates a hot metal suspended at the centre of a closed uniform box. Thermometers E, F, G and H are placed in contact with four sides of the box. Which of the thermometers would register the highest temperature?

A) G B) F C) H D) E

Correct Answer: D) E

A liquid is left in an open dish. After several days, there is less liquid in the dish. Which of the following statements explains this observation?

A) Most energetic molecules leave the surface and return B) Most energetic molecules leave the surface and escape into the air C) Least energetic molecules leave the surface and return D) Least energetic molecules leave the surface and escape into air

Correct Answer: B) Most energetic molecules leave the surface and escape into the air

The color of the visible light region of the electromagnetic spectrum that have the shortest and longest wavelengths respectively are:

A) Red and blue B) Yellow and blue C) Indigo and violet D) Violet and red

Correct Answer: D) Violet and red

Which of the following equations is not a correct mirror formula? [The symbols have their usual meanings]

A) \( N = \frac{360}{\theta} - 1 \) B) \( \frac{1}{f} = \frac{1}{u} + \frac{1}{v} \) C) \( m = \frac{u}{v} \) D) \( f = \frac{1}{D} \)

Correct Answer: D) \( f = \frac{1}{D} \)

An atom in an excited state is one whose:

A) Potential energy is minimum B) Potential energy is maximum C) Electrons are in the conduction band D) Electrons have moved to a higher energy level

Correct Answer: D) Electrons have moved to a higher energy level

The conclusive test for magnetism in a steel bar suspended horizontally at its midpoint is when the bar:

A) Always settles in the magnetic N-S direction B) Always settles in the magnetic E-W direction C) Is repelled by a magnet D) Is attracted by a magnet

Correct Answer: A) Always settles in the magnetic N-S direction

Which of the following devices is used to compare the relative magnitudes of charges on two given bodies?

A) Electrophorus B) Ebonite rod C) Proof plane D) Gold leaf electroscope

Correct Answer: D) Gold leaf electroscope

A direct current cannot pass through a parallel plate capacitor because:

A) The plates are non-conducting B) The plates have equal but opposite charges C) There is a leakage of charge from the plates D) The dielectric between the plates is non-conducting

Correct Answer: D) The dielectric between the plates is non-conducting

The process of producing electric current by a changing magnetic field is referred to as:

A) Flux linkage B) Magnet induction C) Electromagnetic induction D) Electrostatic induction

Correct Answer: C) Electromagnetic induction

The sagging of overhead electrical wires is caused by:

A) Rough handling B) Radiation of heat C) Linear expansion D) Gravitational attraction

Correct Answer: C) Linear expansion

A cell of emf 2 V has an internal resistance of 0.5 Ω. A current of 0.4 A passes through an external resistor, P. Determine the resistance of P.

A) \( 4.5\ \Omega \) B) \( 5\ \Omega \) C) \( 1\ \Omega \) D) \( 4\ \Omega \)

Correct Answer: A) \( 4.5\ \Omega \)

The property of a body that determines the direction of heat flow when the body is in contact with another body is the:

A) Power B) Heat capacity C) Temperature D) Mass

Correct Answer: C) Temperature

In a series R-L-C circuit at resonance, the voltages across the resistor and the inductor are 30 V and 40 V respectively. What is the voltage across the capacitor?

A) 30 V B) 40 V C) 50 V D) 70 V

Correct Answer: B) 40 V

The purpose of commutators in a direct current motor is to:

A) Increase the efficiency of the motor B) Reverse the direction of the current after every half rotation C) Enable a uniform couple to act on the coil D) Increase the number of rotations per second

Correct Answer: B) Reverse the direction of the current after every half rotation

A lead bullet of mass \( 0.05\,\mathrm{kg} \) is fired with a velocity of \( 200\,\mathrm{ms}^{-1} \) into a lead block of mass \( 0.95\,\mathrm{kg} \). Given that the lead block can move freely, the final kinetic energy after impact is:

A) 50 J B) 100 J C) 150 J D) 200 J

Correct Answer: A) 50 J

What is the name given to the force of attraction between the nucleons in the nucleus of an atom?

A) Gravitational force B) Nuclear force C) Electrostatic force D) Magnetic force

Correct Answer: B) Nuclear force

In a controlled thermal fission reactor, the use of control rods will not affect the

A) Speed of the neutrons released on fission B) Rate of production of the neutrons C) Energy generated in the nuclear reactor D) Amount of radiation produced in the nuclear reactor

Correct Answer: D) Amount of radiation produced in the nuclear reactor

The most appropriate value of fuse for a kettle rated 220 V, 1.06 kW is

A) 3A B) 6A C) 5A D) 4A

Correct Answer: C) 5A

The type of mirror used by dentists to inspect the teeth of patients is a

A) Convex mirror B) Concave mirror C) Plane mirror D) Cylindrical mirror

Correct Answer: B) Concave mirror

The diagram below illustrates a mode of vibration of a wire of length 125cm. The speed of the waves along the wire is 120m/s. Use the diagram below to answer questions 39 and 40

From the diagram above, determine the wavelength of the wave

A) 0.25 m B) 0.50 m C) 0.75 m D) 1.00 m

Correct Answer: B) 0.50 m

From the diagram above, determine the frequency of the waves.

A) 24 Hz B) 192 Hz C) 240 Hz D) 286 Hz

Correct Answer: C) 240 Hz

Which of the following statements about the properties of the electric field produced by charged parallel plates is not correct?

A) The electric field in the region outside the parallel plate is zero, except for the edge effects B) The magnitude of the electric field strength at any point between the plates, except near the edges, depends on the magnitude of the charge on each plate. C) The magnitude of the electric field strength at any point between the plates is directly proportional to the magnitude of the charge on each plate. D) The electric field is uniform everywhere in the space between the parallel plates

Correct Answer: C) The magnitude of the electric field strength at any point between the plates is directly proportional to the magnitude of the charge on each plate.

A car, P, with a velocity of 30 m/s is traveling in the same direction as a car, Q, with a velocity of 20 m/s. The velocity of P relative to Q is

A) 50 m/s B) 45 m/s C) 20 m/s D) 10 m/s

Correct Answer: D) 10 m/s

The range of wavelengths of the infrared waves in an electromagnetic spectrum is \( 10^{-3} \, \text{m} \) to \( 10^{-6} \, \text{m} \). The wavelength of the radiation is

A) longer than \( 10^{-6} \, \text{m} \) B) shorter than \( 10^{-6} \, \text{m} \) C) shorter than \( 10^{3} \, \text{m} \) D) longer than \( 10^{3} \, \text{m} \)

Correct Answer: A) longer than \( 10^{-6} \, \text{m} \)

When an electron jumps directly from an orbit of \( n = 4 \) to \( n = 2 \),

A) A photon is emitted B) A photon is absorbed C) Two photons are emitted D) Two photons are absorbed

Correct Answer: A) A photon is emitted

When a light-weight body and a massive body are acted upon by the same force for the same period of time, the

A) Momenta of both bodies remain the same B) Lighter body has a higher momentum C) Massive body has a higher momentum D) Massive body builds up a higher velocity

Correct Answer: A) Momenta of both bodies remain the same

Which of the following devices is associated with alternating currents only?

A) Induction coil B) Lead-acid accumulator C) Step up transformer D) Moving-coil galvanometer

Correct Answer: C) Step up transformer

A body starts with an initial velocity of 20 m/s and moves with a uniform acceleration, \( a \), for 15 seconds. Which of the following equations represents the distance, \( S \), traveled?

A) \( S = 300 + \frac{225}{2}a \) B) \( S = 300 + \frac{2a}{225} \) C) \( S = 300 + \frac{225a}{2} \) D) \( S = 300a + \frac{225}{2} \)

Correct Answer: C) \( S = 300 + \frac{225a}{2} \)

The ratio of maximum range to maximum height of a projectile is 4. Determine the angle of projection.

A) 30° B) 60° C) 45° D) 0°

Correct Answer: C) 45°

Which of the following statements is/are correct about the forces in towing a bus?

A) II, III and IV B) II only C) I, II and III only D) I only

Correct Answer: B) II only

The diagram below illustrates a velocity-time graph. Determine the distance between X and Y.

A) 10.0 m B) 40.0 m C) 80.0 m D) 160.0 m

Correct Answer: D) 160.0 m

Theory Questions

The force, F, acting on the wings of an aircraft moving through the air of velocity, v, and density, ρ, is given by the equation F = kvxρyAz , where k is a dimensionless constant and A is the surface area of the wings of the aircraft. Use dimensional analysis to determine the values of x, y, and z.

Define strain energy.

Write an expression for the energy stored, E, in a stretched wire of original length, l , cross-sectional area, A, extension, e, and Young's modulus, Y, of the material of the wire.

a. A projectile is fired at an angle, θ, to the horizontal with velocity, u. Show that at any time, t, during the motion, the:
i. horizontal component of the velocity is independent of t;
ii. vertical component of the velocity depends on t.
b. State the assumption on which projectile motion is based.

State three differences between geostationary satellites and polar satellites.

a. Using the kinetic theory, explain the term diffusion of fluid molecules

Name one phenomenon that demonstrates that light behaves as a:
i. wave
ii. particles

a. State one difference between an intrinsic and an extrinsic semiconductor

b. Draw a circuit diagram to illustrate full wave smoothing rectification.

a. What is fibre optics?

b. State two reasons why optical fibres are preferred to copper cables in the telecommunication industry.

ai. State the reason why simple harmonic motion is periodic.
ii. State two factors that affect the period of oscillation of a simple pendulum.
iii. Sketch a graph of the total mechanical energy, E, against displacement, y, for the motion of a simple pendulum from one extreme position to the other.
b. The diagram above illustrates an oscillatory pendulum. Calculate the work done in raising the pendulum to point B, if the mass of the bob is 50 g. [g = 10ms2 ] see the figure above
c. A spiral spring of spring constant, k, and natural length, l, has a scale pan of mass 0.04 kg hanging on its lower end while the upper end is firmly fixed to a support. When an object of mass 0.20 kg is placed on the scale pan, the length of the spring becomes 0.055 m and when the object is replaced with another object of mass 0.28 kg, the length of the spring becomes 0.065 m. Calculate the values of k and l. [g = 10ms2 ]

a. Define each of the following terms used with simple machines:
i. Pivot ii.Load iii. Efficiency. b. A truck of mass 1.2 × 103 kg is pulled from rest by a constant horizontal force of 25.2N on a leveled road. If the maximum speed attainable in the process is 60 km/h. Calculate the: i. work done by the force; ii. distance traveled by the truck in reaching the maximum speed.
c. State two differences between absolute zero temperature and ice point.
d. An uncalibrated liquid-in-glass thermometer was used in determining a Celsius temperature. The readings are tabulated below

Temperature/°C	-6	0	100
Length of column/ cm	L	2.0	15.0

ai. Why are parabolic mirrors suitable for use in the headlamps of vehicles?
ii. Draw a ray diagram to illustrate the answer in 10(a)(i).
bi. State two applications of echoes.
ii. An observer standing at a point, P, on the same horizontal ground as the foot, H, of a tower, shouts, and 1.20 s later, he hears the echo. He then moved to another point, Q, 40 m from P, and shouted again but the echo was heard after 1.45 s. Calculate the:
I. distance between P and H;
II. speed of sound in air.
ci. Define the term absolute refractive index of a medium.
ii. A piece of coin falls accidentally into a tank containing two immiscible liquids A and B as illustrated in Fig. 10.0 above.

Calculate the displacement of the coin when viewed vertically from above. [refractive index of A = 1.3, refractive index of B = 1.4]

ai. Define the electric potential at a point in an electric field.
ii. An uncharged body, A, was charged electrostatically by a test charge, B, using the method of induction and the method of contact. State two differences between the two methods.
b. An important precaution during an electricity experiment is to open the circuit when no readings are being taken. Give two reasons for the stated precaution.
ci. Fig. 11.0 is a circuit diagram in which a coil of inductance, L, and a resistor of resistance, R, are connected to a variable alternating source of frequency, f. The table shows the square of the impedance, Z2 ; corresponding to each value of ƒ2.

Write down the equation for Z in terms of f2 , R2 , and L2 .
ii. Plot a graph Z2against\(f2 of and use it to determine the values of:
i. L
ii. R [π2 = 10]

a. State the function of each of the following parts of a modern x-ray tube: i. heater; ii. high tension source; iii. cooling fins.
b. State one reason for each of the following design features of a modern x-ray tube:
i. the glass envelope is highly evacuated;
ii the target is a metal of very high melting point;
iii. the cooling fins are located outside the glass envelope.
c. In a nuclear fission reaction, a nuclide 235U92 is bombarded with a neutron to produce 93Kr36 and 141Ba56 with additional neutrons, the energy involved in the process is Q. [mass of 235U92 = 235.044 u, mass of 93Kr36 = 91.898 u, mass of 141Ba56 = 140.914 u, mass of neutron = 1.009u, 1u = 1.66×10−27 kg, c = 3.0 × 108ms1 ]
i. Write down the balanced nuclear reaction equation for the process.
ii. State with reason whether Q is absorbed or released in the process.
iii. Calculate the value of Q in joules.