Physics 2019

Objective Questions

The time rate of increase in velocity is called

A. speed. B. force. C. momentum. D. acceleration.

Correct Answer: D. acceleration

Which of the following quantities is a vector?

A. Speed B. Volume C. Momentum D. Energy

Correct Answer: C. Momentum

In an elastic collision, momentum is conserved as well as

A. speed. B. velocity. C. kinetic energy D. potential energy.

Correct Answer: C. kinetic energy

The induced current in a coil always flows in a direction so as to oppose the change causing it. This statement is known as

A. Ampere's law. B. Coulomb's law. C. Lenz's law. D. Faraday's law.

Correct Answer: C. Lenz's law

Which of the following instruments can be used to compare the magnitudes of charges on two given bodies?

A. Proof plane B. Gold-leaf electroscope C. The electrophorus D. Ebonite rod

Correct Answer: B. Gold-leaf electroscope

A body of mass 2kg is released from a point 100 m above the ground level. Calculate its kinetic energy 80 m from the point of release. [g = 10 m s^-2]

A. 900 J B. 1600 J C. 200 J D. 600 J

Correct Answer: B. 1600 J

Which of the following waves is not mechanical?

A. Water waves B. Waves in pipes C. Sound waves D. Radio waves

Correct Answer: D. Radio waves

A loaded spring is set in simple harmonic motion. The force that tends to restore the load to its equilibrium position is

A. elastic. B. gravitational. C. frictional. D. adhesive.

Correct Answer: D. adhesive

Which of the following situations cannot produce total internal reflection? A light ray travelling from

A. water to kerosene. B. glass to water. C. water to air. D. Air to water.

Correct Answer: A. water to kerosene

The vacuum in a thermos flask reduces heat loss resulting from

A. conduction only. B. conduction and convection only. C. radiation only. D. radiation and Convection only.

Correct Answer: B. conduction and convection only

The diagram above represents an experimental set-up for verifying

A. mirror formula. B. lens formula. C. laws of refraction. D. laws of reflection

Correct Answer: D. laws of reflection

Which of the following statements about a moving object is correct?

A. At a steady speed, the air resistance on it must be equal to zero. B. When accelerating, the resultant force acting on it must be equal to zero. C. There must always be a resultant force acting on it. D. At a steady speed, the resultant force acting on it must be equal to zero.

Correct Answer: D. At a steady speed, the resultant force acting on it must be equal to zero

The efficiency of a transformer is 100 %. Which of the following equations would be correct?

A. IpEs = IsEp B. NpEp = NsEs C. NsIp = NpIs D. NsIs = NpIp

Correct Answer: C. NsIp = NpIs

A freshly demagnetized bar magnet is placid In East-West direction to ensure that,

A. it is affected by the earth's magnetic field. B. the magnetic domains are within the earth's field. C. magnetic domains remain randomly arranged. D. magnetic domains are orderly aligned

Correct Answer: D. magnetic domains are orderly aligned

Which of the following graphs correctly represents the plot of the charge Q against the potential difference V in a capacitor?

A. Graph A B. Graph B C. Graph C D. Graph D

Correct Answer: B. Graph B

A small amount of air is introduced into the vacuum above the mercury in a mercury barometer tube. The mercury level fails because the air molecules

A. cool the mercury and make it contract. B. heat the mercury and make it lighter. C. increase the pressure above the mercury. D. decrease the pressure above the mercury.

Correct Answer: C. increase the pressure above the mercury

Calculate the quantity of heat needed to change 60 g of ice at 0.0 °C to water at 80.0 °C. [Specific latent heat of fusion of ice = 3.36 x 10⁵ J kg^-1, specific heat capacity of water = 4.2 x 10³ J kg^-1 K^-1]

A. 22.17 kJ B. 40.32 kJ C. 4.80 kJ D. 20.16 kJ

Correct Answer: B. 40.32 kJ

The wire of a platinum resistance thermometer has a resistance of 3.5 Ω at 0 °C and 10.5 Ω at 100 °C. Calculate the temperature of the wire when its resistance is 7.5 Ω.

A. 57°C B. 78°C C. 25°C D. 36°C

Correct Answer: A. 57°C

A transverse wave of frequency 9 Hz travels 4.5 m in 0.6 s. Calculate the wavelength of the wave.

A. 1.20m B. 3.33m C. 0.30m D. 0.83m

Correct Answer: D. 0.83m

The speed of sound is least in which of the following media?

A. Wood B. Air C. Brass D. Water

Correct Answer: B. Air

Which of the following characteristics of waves can be demonstrated using a ripple tank? I. Reflection II. Refraction III. Diffraction

A. I only B. II only C. I and II only D. I, II and III

Correct Answer: D. I, II and III

Which of the following graphs gives the correct relationship between energy and mass when mass is converted to energy?

A. Graph A B. Graph B C. Graph C D. Graph D

Correct Answer: B. Graph B

An 800 kg car moving at 80 km h^-1 collides with a 1200 kg car moving at 40 km h^-1 in the same direction. If the cars stick together, calculate their common speed.

A. 56 km h^-1 B. 60 km h^-1 C. 8 km h^-1 D. 40 km h^-1

Correct Answer: A. 56 km h^-1

The mass of an object is doubled while the force acting on it is halved. The resulting acceleration of the object is

A. doubled. B. quadrupled. C. quartered. D. halved.

Correct Answer: C. quartered

the maximum and minimum thermometer reads the

A. maximum temperature during the day and minimum temperature at night from the time it was lest reset B. maximum temperature at night and minimum temperature during the day from the time it was last reset. C. maximum temperature during the day and minimum temperature at night at all times. D. maximum temperature at night and minimum temperature during the day at all times.

Correct Answer: C. maximum temperature during the day and minimum temperature at night at all times

An a.c. generator can be converted to a d.c. generator by replacing the

A. commutator with slip rings. B. slip rings with a commutator. C. commutator with an armature. D. armature with a commutator.

Correct Answer: B. slip rings with a commutator

Which of the following statements is the correct reason for which soft iron is used in making the armature of an electric bell? Soft iron

A. retains it magnetism for a long time. B. is a diamagnetic material. C. loses its magnetism easily. D. is not easily magnetized.

Correct Answer: C. loses its magnetism easily

The diagram above illustrates a metre bridge circuit under balanced condition.

Determine the value of x.

A. 57.2cm B. 71.4cm C. 10.0 cm D. 28.6cm

Correct Answer: D. 28.6cm

Which of the following devices is used for storing electric charge?

A. Capacitor B. Transformer C. Ammeter D. Potentiometer

Correct Answer: A. Capacitor

An electron of mass 9.1 x 10^-31 kg moves with a speed of 2.0 x 10⁶ m s^-1 round the nucleus of an atom in a circular path of radius 6.1 x 10^-11 m. Use this information to answer questions 30 and 31.

Determine the angular speed of the electron.

A. 5.22 x10¹⁵ rad s^-1 B. 3.28 x 10¹⁶ rad s^-1 C. 8.55 x 10³ rad s^-1 D. 9.11 x 10¹³ rad s^-1

Correct Answer: B. 3.28 x 10¹⁶ rad s^-1

Calculate the centripetal force acting on the electron.

A. 1.3 x 10^-26 N B. 7.7 x 10^-47 N C. 6.0 x 10^-8 N D. 3.0 x 10^-14 N

Correct Answer: C. 6.0 x 10^-8 N

A device consumes 100 W of power when connected to a 120 V source. Calculate its resistance.

A. 144 Ω B. 1.2 Ω C. 12000 Ω D. 20 Ω

Correct Answer: A. 144 Ω

Which property of a wave remains constant When the wave travels cm one medium into another?

A. Frequency B. Amplitude C. Wavelength D. Velocity

Correct Answer: A. Frequency

The anomalous expansion of water occurs in the range

A. 0 ^oC to 100 ^oC B. 0 ^oC to 4 ^oC C. 4 ^oC to 100 ^oC D. -4 ^oC to 0 ^oC

Correct Answer: B. 0 ^oC to 4 ^oC

A ray of light travelling from a rectangular glass block of refractive index 1.5 into air, strikes the block air boundary at an incident angle of 30^o. Calculate the angle of refraction.

A. 45.0° B. 48.6° C. 20.0° D. 19.5°

Correct Answer: D. 19.5°

A rectangular piece of iron measuring 4 cm x 3 cm at 20°C is heated until its temperature increases by 100°C. Calculate the new area of the meatal of the metal. [Linear expansivity of iron = 1.2 x 10^-5 K^-1]

A. 12.0173 cm² B. 12.0144 cm² C. 12.0346 cm² D. 12.0288 cm²

Correct Answer: A. 12.0173 cm²

Two bodies of masses 3.0 kg and 2.0 kg are 50 cm apart. Calculate the force of attraction between them. [G= 6.67 x 10^-11 N m² kg^-2]

A. 5.0 x 10 N B. 1.6 x 10^-9 N C. 1.3 x 10³ N D. 2.3 x 10³ N

Correct Answer: B. 1.6 x 10^-9 N

The diagram above illustrates an object moving in a circular path at constant speed. Which of the arrows correctly indicate the direction of linear velocity?

A. W B. Z C. X D. Y

Correct Answer: B. Z

Which of the following thermometers is used to measure the temperature of the human body?

A. Platinum resistance thermometer B. Thermocouple C. Alcohol-in-glass thermometer D. Gas thermometer

Correct Answer: C. Alcohol-in-glass thermometer

In the diagram above, the time taken to trace a wave between P and Q is

A. 1 ½ periods. B. 2 periods. C. 1 period. D. 1 ¼ periods.

Correct Answer: A. 1 ½ periods

Which of the following components does not serve as a safety device in electrical circuits?

A. Earth wire B. Connecting wires C. Fuse D. Switch

Correct Answer: B. Connecting wires

Which of the following liquids has the highest surface tension?

A. Oily water B. Soapy water C. Cold water D. Hot water

Correct Answer: C. Cold water

The nucleon and proton numbers of a neutral atom of an element are 238 and 92 respectively. Determine the number of neutrons in the atom.

A. 146 B. 119 C. 330 D. 165

Correct Answer: A. 146

An instrument used to measure relative humidity is the

A. manometer. B. hygrometer. C. hydrometer. D. pyrometer.

Correct Answer: B. hygrometer

The area under a velocity-time graph represents

A. distance. B. speed. C. acceleration. D. moment.

Correct Answer: A. distance

Which of the following statements about neutral atom is correct? The

A. number of protons is equal to that of electrons. B. core is composed of electrons and protons. C. number of electrons is equal to that of neutrons. D. number of neutrons is equal to that of protons.

Correct Answer: A. number of protons is equal to that of electrons

The property that is not exhibited by sound waves is

A. reflection B. diffraction. C. polarization. D. interference.

Correct Answer: C. polarization

When ultraviolet light is incident on the surface of certain metals, particles are emitted. These particles are called

A. photoelectrons. B. positrons. C. protons. D. photons

Correct Answer: A. photoelectrons

Niels Bohr drew certain conclusions about the structure of the atom. Which of the following statements is one of those conclusions?

A. The orbit with the least energy is the farthest from the nucleus. B. The allowed orbits contain the same number of electrons. C. Within an atom, there are certain allowed orbits. D. All of the orbits represent the same amount of energy.

Correct Answer: C. Within an atom, there are certain allowed orbits

The graph above illustrates the variation of temperature with time for a solid that is being heated. Which processes take place at the segments P and Q respectively?

A. Condensation and evaporation B. Freezing and evaporation C. Evaporation and solidification D. Melting and boiling

Correct Answer: D. Melting and boiling

Theory Questions

A stone of mass 20g is released from a catapult whose rubber is stretched through 5cm. If the force constant of the rubber is 200Nm-1, calculate the speed with which the stone leaves the catapult.

The diagram below illustrates a projectile motion.

Identify each of the physical quantities labelled P, β, H and R.
Write an equation to show the relationship between P, g and R_max, where g is the acceleration due to gravity and R_max is maximum R.

State three observable phenomena in which waves behave like a particle.

List three magnetic elements that determine the earth’s magnetic field at a point.

Explain this term as used in Electronics:

Free electrons
Holes

State the principle of operation of fibre optics
State two applications of fibre optics in medicine

Define diffusion
State two factors that affect the rate of diffusion

State Newton’s Law of Universal Gravitation
Define gravitational field

Derive the equation relating the universal gravitational constant, G, and the acceleration of free fall, g, at the surface of the earth from Newton’s law of universal gravitation
State two assumptions for which the relationship in 8(b)(i) holds

Calculate the force of attraction between a star of mass 2.00 × 1030 kg and the earth assuming the star is located 1.50 × 1080km from the earth.
[Mass of the earth = 5.98 × 1024kg, G = 6.67 × 10-11Nm2kg-2, g = 10ms-2]

Define escape velocity
State two differences between the acceleration of free fall (g) and the universal gravitational constant (G).

Explain latent heat
State two factors that affect the rate of evaporation of a liquid

Explain this observation:
On a dry day, water in a clay pot is cooler than water in a closed plastic container.
Explain this observation:
Food gets cooked faster in a pressure cooker than in an ordinary cooking pot.

State two effects of heat on a substance
A 40V electric heater is used to supply a current of 12A for 1400s to a body of mass 1.5kg at the melting point of the body. The body melts and its temperature rises through 60°C in an extra 72s.

Determine the latent heat of fusion of the body.
Determine the specific heat capacity of the body.

Define atomic spectra
Differentiate between emission spectra and absorption spectra

The diagram above illustrates an electron transition from energy level n = 3 to n = 1.

Calculate the energy of the photon
Calculate the frequency of the photon
Calculate the wavelength of the photon

Differentiate between soft x-rays and hard x-rays
Draw the circuit symbol for a p – n junction diode
Give the reason for doping a semiconductor material

Define force and state its S. I. unit
List the two types of solid friction

A car travelling at a constant speed of 30 ms-1 for 20s was suddenly decelerated when the driver sighted a pot-hole. It took the driver 6s to get to the pot-hole with a reduced speed of 18ms-1. He maintained the steady speed for another 10s to cross the pot-hole. The brakes were then applied and the car came to rest 5s later.

Draw the velocity-time graph for the journey
Calculate the deceleration during the last 5s of the journey
Calculate the total distance covered

The diagram above illustrates a structure of a typical photocell. Identify each of the parts labelled A and B.
State one function for each of A and B
Einstein’s photoelectric equation can be written as E = hf – Wo. State what each of the terms E, hf, and Wo represents.

A photon is incident on a metal whose work function is 1.32eV. An electron is emitted from the surface with a maximum kinetic energy of 1.97 eV. Calculate the frequency of the photon.
[1ev = 1.6 x 10-19]

Define half-life of a radioactive element
Sketch a graph of the relation N = N0e–λt Sketch a graph of the relation N = N0e–λt

Practical Questions

You are provided with a stopwatch, a meter rule, a split cork, retort stand and clamp, a pendulum bob, a piece of thread and other necessary apparatus.
1. Place the retort stand on a laboratory stool. Clamp the split cork.
2. Suspend the pendulum bob from the split cork such that the point of support P of the bob is at a height H = 100 cm above the floor Q. The bob should not touch the floor and H should be kept constant throughout the experiment.
3. Adjust the length of the thread such that the centre A of the bob is at a height y = AQ = 20 cm from the floor.
4. Displace the bob such that it oscillates in a horizontal plane.
5. Take the time t for 20 complete oscillations.
6. Determine the period T of oscillation and evaluate T².
7. Repeat the procedure for four other values of y =30 cm, 40 cm, 50 cm and 60 cm. In each case, determine T and T².
8. Tabulate the results.
9. Plot a graph of T² n the vertical axis and y on the horizontal axis, starting both axes from the origin (0, 0).
10. Determine the slope, s, of the graph and the intercept c on the vertical axis.
11. If in this experiment, SR = c, calculate R.
12. State two precautions taken to ensure accurate results.
1. The bob of a simple pendulum is displaced a small distance from the equilibrium position and then released to perform simple harmonic motion.
  Identify where its:
  1. kinetic energy is maximum;
  2. acceleration is maximum.
2. An object of weight 120 N vibrates with a period of 4.0 s when hung from a spring. Calculate the force per unit length of the spring.
  [g = 10 ms^-2, π = 3.142]

You are provided with a converging lens and holder; a screen, a ray box containing an illuminated object pin and a meter rule.
1. Place the lens in its holder such that it is facing a distant object seen through a well-lit laboratory window. Move the screen to and fro until a sharp image of the distant object is formed on it. Measure the distance, fo , between the screen and the lens.
2. Clamp the meter rule securely to the table.
3. Place the illuminated object pin at the end R of the meter rule. Place the lens at a position P such that X = RP = 20 cm.
4. Move the screen to a position Q to receive a sharp image of the object. Measure the distance Y = PQ.
5. Evaluate Z = (X + Y).
6. Repeat the procedure for five other values of x = 25 cm, 30 cm, 40 cm and 45 cm. In each case, record X, Y and evaluate Z.
7. Tabulate the results.
8. Plot a graph with Z on the vertical axis and X on the horizontal axis. Draw a smooth curve through the points.
9. Determine from your graph the minimum value of Z = Zo and its corresponding distance Xo.
10. Evaluate W = ½(Zo/4+Xo/2)
11. State two precautions taken to ensure accurate results.
1. Draw a ray diagram to show how a convex lens forms an image of magnification less than one.
2. Name two pairs of features in the human eye and a lens camera that performs similar functions.

You are provided with a battery of e.m.f. E, a key K, a voltmeter, a standard resistor Ro = 2, a resistance box R and some connecting wires.
1. Measure and record the e.m.f. E of the battery.
2. Set up a circuit as shown in the diagram above with the key open.
3. Set the resistance on the resistance box to R = 2.
4. Close the key, read and record the potential difference V on the voltmeter.
5. Evaluate V-1.
6. Repeat the procedures for five other values of R = 5 Ω, 10 Ω, 12 Ω, 15 Ω and 20 Ω. In each case, record V and evaluate V-1.
7. Tabulate the results.
8. Plot a graph with R on the vertical axis and V-1 on the horizontal axis, starting both axes from the origin (0, 0)
9. Determine the slope, s, of the graph and the intercept c on the vertical axis.
10. Calculate α and β from the equations s = Ro α and c = - (Ro + B).
11. State two precautions taken to ensure accurate results.

1. In the circuit diagram above, the battery has negligible internal resistance. Calculate the power dissipated as heat in the section AB of the circuit.
2. An electric equipment of power rating 3.6 kW is to be connected to a 240 V line whose circuit breaker is rated 20 A. Justify whether or not the breaker would open when the equipment is switched on. [4 marks]