JAMB Physics 1985 past questions and answers

Which of the following is NOT a fundamental S.I. unit?

1. A.Metre
2. B.Ampere
3. C.Kelvin
4. D.Second
5. E.Radian

A simple pendulum with a period of 2.0 s has its length doubled. Its new period is

1. A.1.00 s
2. B.1.41 s
3. C.0.35 s
4. D.2.83 s
5. E.4.00 s.

Which of the following statements are true about the spring balance and the chemical balance? I. Both are used to measure the mass of an object II. Either of them may be used to measure the weight of an object. III. The spring balance works on the principle of Hooke's law while the chemical balance works on the principle of moments. IV. A change in gravity changes the readings of a spring balance but not that of a chemical balance

1. A.I and IV
2. B.II and III
3. C.III and IV
4. D.I, II and III
5. E.I and III.

Which of the following types of motion are oscillatory? I. A diving board when used by a diver II. The motion of the balance wheel of a wrist watch III. The motion of the turn-table of a record player IV. The motion of the centre of a ten kobo piece as it rolls down an inclined plane. V. The motion of the needle of a D.C. ammeter into which a low A.C. current is passed

1. A.I and II only
2. B.I, II and III
3. C.II, III and IV
4. D.I, II and V
5. E.III, IV and V

The graph in Fig. 1 above describes the motion of a particle. The acceleration of the particle during the motion is

1. A.0.00 m s⁻²
2. B.0.25 m s⁻²
3. C.4.00 m s⁻²
4. D.8.00 m s⁻²
5. E.10.00 m s⁻².

If a car starts from rest and moves with a uniform acceleration of 10 m s⁻² for ten seconds, the distance it covers in the last one second of its motion is

1. A.95 m
2. B.100 m
3. C.500 m
4. D.905 m
5. E.1000 m

A block of mass 2.0 kg resting on a smooth horizontal plane is acted upon simultaneously by two forces, 10 N due North and 10 N due East. The magnitude of the acceleration produced by the forces on the block is

1. A.0.10 m s⁻²
2. B.7.05 m s⁻²
3. C.10.00 m s⁻²
4. D.14.10 m s⁻²
5. E.20.00 m s⁻²

A metal block of mass 5 kg lies on a rough horizontal platform. If a horizontal force of 8 N applied to the block through its centre of mass just slides the block on the platform, then the coefficient of limiting friction between the block and the platform is

1. A.0.16
2. B.0.63
3. C.0.80
4. D.1.60
5. E.2.00

Which of the following is NOT a force?

1. A.Friction
2. B.Tension
3. C.Upthrust
4. D.Weight
5. E.Impulse

Two masses 40 g and 60 g respectively, are attached firmly to the ends of a light metre rule. The centre of gravity of the system is

1. A.at the mid-point of the metre rule
2. B.40 cm from the lighter mass
3. C.40 cm from the heavier mass
4. D.60 cm from the heavier mass
5. E.indeterminate because the metre-rule is light.

A 0.05 kg bullet travelling at 500 m s⁻¹ horizontally strikes a thick vertical wall. It stops after penetrating through the wall a horizontal distance of 0.25 m. What is the magnitude of the average force the wall exerts on the bullet?

1. A.25 N
2. B.50 N
3. C.250 N
4. D.5000 N
5. E.25 000 N

A force of 100 N stretches an elastic string to a total length of 20 cm. If an additional force of 100 N stretches the string 5 cm further, find the natural length of the string.

1. A.15 cm
2. B.12 cm
3. C.10 cm
4. D.8 cm
5. E.5 cm

Two divers G and H are at depths 20 m and 40 m respectively below the water surface in a lake. The pressure on G is P₁ while the pressure on H is P₂. If the atmospheric pressure is equivalent to 10 m of water, then the value of P₂/P₁ is

1. A.0.50
2. B.0.60
3. C.1.67
4. D.2.00
5. E.3.00

The areas of the effort and load pistons of a hydraulic press are 0.5 m² and 5 m² respectively. If a force F₁ of 100 N is applied on the effort piston, the force F₂ on the load is

1. A.10 N
2. B.100 N
3. C.500 N
4. D.1000 N
5. E.5000 N

A metal cube of volume 10³ mm³ is lowered into a measuring cylinder containing water. If the internal cross-sectional area of the cylinder is 1.5 × 10² mm², by how much does the water level rise in the cylinder?

1. A.6.67 × 10⁰ mm
2. B.5.50 × 10² mm
3. C.1.15 × 10³ mm
4. D.2.50 × 10³ mm
5. E.1.50 × 10⁵ mm

A uniform cylindrical block of wood floats in water with one-third of its height above the water level. In a liquid of relative density 0.8, what fraction of its height will be above the liquid level?

1. A.1/6
2. B.1/5
3. C.1/3
4. D.4/5
5. E.5/6.

A thin aluminium plate has a surface area of 1.500 m² at 20°C. What will be its surface area when it is cooled to −20°C? (Take the linear expansivity of aluminium to be 2.5 × 10⁻⁵ K⁻¹).

1. A.1.503 m²
2. B.1.500 m²
3. C.1.498 m²
4. D.1.497 m²
5. E.1.490 m².

Two liquids, P at a temperature of 20°C and Q at a temperature of 80°C have specific heat capacities of 1.0 J kg⁻¹ °C⁻¹ and 1.5 J kg⁻¹ °C⁻¹ respectively. If equal masses of P and Q are mixed in a lagged calorimeter, then the equilibrium temperature is

1. A.44°C
2. B.50°C
3. C.56°C
4. D.60°C
5. E.70°C.

A quantity of gas occupies a certain volume when the temperature is −73°C and the pressure is 1.5 atmospheres. If the pressure is increased to 4.5 atmospheres and the volume is halved at the same time, what will be the new temperature of the gas?

1. A.573°C
2. B.327°C
3. C.300°C
4. D.110°C
5. E.27°C

In a gas experiment, the pressure of the gas is plotted against the reciprocal of the volume of the gas at a constant temperature. The unit of the slope of the resulting curve is

1. A.force
2. B.force/m
3. C.work
4. D.force/m³
5. E.energy/m².

Water shows anomalous behaviour

1. A.below 0°C
2. B.between 0°C and 4°C
3. C.at exactly 4°C
4. D.between 4°C and 100°C
5. E.above 100°C

Two thermos flasks of volume V_x and V_y are filled with liquid water at an initial temperature of 0°C. After some time the temperature were found to be θ_x, θ_y respectively. Given that V_x/V_y = 2 and θ_x/θ_y = ½, the ratio of the heat flow into the flasks is

1. A.¼
2. B.½
3. C.4
4. D.1
5. E.2

A good calorimeter should be of

1. A.low specific heat capacity and low heat conductivity
2. B.low specific heat capacity and high heat conductivity
3. C.high specific heat capacity and low heat conductivity
4. D.high specific heat capacity and low heat conductivity
5. E.dull surface and low heat conductivity.

Which of the following statements is NOT correct?

1. A.Boiling occurs when the saturated vapour pressure of the liquid involved equals the external pressure
2. B.Both the boiling point and the saturated vapour pressure of a given liquid depend on the external pressure
3. C.The saturated vapour pressure rises with increase in temperature
4. D.The saturated vapour pressure is independent of the volume available for the vapour.
5. E.It is possible to boil water at a lower temperature than 100°C at high altitude.

Which of the following phenomena CANNOT be explained by the molecular theory of matter?

1. A.Expansion
2. B.Conduction
3. C.Convection
4. D.Radiation
5. E.Evaporation

In order to find the depth of the sea, a ship sends out a sound wave and receives an echo after one second. If the velocity of sound in water is 1500 m/s, what is the depth of the sea?

1. A.0.75 km
2. B.1.50 km
3. C.2.20 km
4. D.3.00 km
5. E.3.75 km

When a sound wave passes from air into water its

1. A.speed and frequency increase but its wavelength remains the same
2. B.speed and wavelength increase but its frequency remains the same
3. C.speed decreases
4. D.speed remains the same but its frequency and wavelength change
5. E.speed increases but its frequency and wavelength decrease.

If the fundamental frequency of a closed pipe organ on a day when the speed of sound is 340 m s⁻¹ is 170 Hz, then the length of the pipe is

1. A.50 cm
2. B.70 cm
3. C.100 cm
4. D.150 cm
5. E.200 cm

An object is placed 15 cm in front of a concave mirror of radius 40 cm. The image formed is

1. A.virtual and 60 cm behind the mirror
2. B.real and 60 cm in front of the mirror
3. C.virtual and at infinity
4. D.real and at infinity
5. E.virtual and 40 cm from the mirror.

A 45° triangular glass prism can be used as a reflector of light because

1. A.refraction never takes place in such a prism
2. B.the angle of reflection equals the angle of incidence
3. C.the refractive index of glass is less than 1
4. D.It is transparent
5. E.the critical angle for glass is less than 45°.

A convex mirror is used as a driving mirror because I. Its image is erect II. It has a large field of view III. It has a long focal length. Identify the CORRECT statement(s).

1. A.I and III only
2. B.I and II only
3. C.II and III only
4. D.I, II and III only
5. E.I only

Two rays of light from a point below the surface of water are equally inclined to the vertical and are inclined to each other at 60° in water. What is the angle between the rays when they emerge into air? (Take the refractive index of water to be 4/3)

1. A.41.8°
2. B.44.1°
3. C.60.0°
4. D.83.6°
5. E.120.0°

A narrow beam of white light can be split up into different colours by a glass prism. The correct explanation is that

1. A.white light is an electromagnetic wave
2. B.the prism has all the colours of the white light
3. C.white light has undergone total internal reflection in the prism
4. D.different colours of white light travel with different speeds in glass
5. E.white light consists of yellow, green and red colours.

A charge of one coulomb liberates 0.0033 g of copper in an electrolytic process. How long will it take a current of 2 A to librate 1.98 g of copper in such a process?

1. A.5 minutes
2. B.30 minutes
3. C.50 minutes
4. D.60 minutes
5. E.120 minutes

If the distance between two stationary charged particles is doubled, the magnitude of the electrostatic force between them will be

1. A.doubled
2. B.halved
3. C.a quarter of its former value
4. D.unchanged
5. E.four times the original value.

Which of the following methods CANNOT be used to produce a steel magnet? The

1. A.passing of an electric current through a solenoid
2. B.repeated stroking of the specimen with a magnet
3. C.repeated stroking of the specimen in opposite directions with two magnets
4. D.heating of the specimen
5. E.hammering of the specimen in the earth's magnetic field.

A cell gives a current of 0.15 A through a resistance of 8 Ω and 0.3 A when the resistance is changed to 3 Ω. The internal resistance of the cell is

1. A.0.05 Ω
2. B.1.00 Ω
3. C.1.50 Ω
4. D.2.00 Ω
5. E.2.50 Ω

Which of the following will convert a milliammeter to a voltmeter?

1. A.Low series resistance
2. B.Low parallel resistance
3. C.High series resistance
4. D.High parallel resistance
5. E.Parallel resistance equal to milliammeter resistance.

Which of the graphs A − E (Fig. 3) represents the current-voltage (I − V) relationship for a cell with internal resistance?

1. A.A
2. B.B
3. C.C
4. D.D
5. E.E

A wire P has half the diameter and half the length of a wire Q of similar material. The ratio of the resistance of P to that of Q is

1. A.8 : 1
2. B.4 : 1
3. C.2 : 1
4. D.1 : 1
5. E.1 : 4

An electric kettle, connected to a 240 V mains, produces 6.0 × 10⁵ J of heat energy to boil a quantity of water in 5 minutes. Find the resistance of the kettle.

1. A.14.4 Ω
2. B.28.8 Ω
3. C.144 Ω
4. D.288 Ω
5. E.2880 Ω

On which of the following does the operation of a moving coil ammeter depend? I. Electromagnetic induction II. Force on a current-carrying conductor in a magnetic field. III. Magnetic effect of an electric current

1. A.I only
2. B.II only
3. C.III only
4. D.II and III
5. E.I, II and III.

In Fig. 4, current (I) passes through the parallel combination. If the power dissipated in the 5 Ω resistor is 40 W, then the power dissipated in the 10 Ω resistor is

1. A.10 W
2. B.20 W
3. C.40 W
4. D.80 W
5. E.100 W

Which of the following statements is NOT correct?

1. A.A galvanometer can be converted to an ammeter with a different range by connecting a high resistance in series
2. B.An electric current always produces a magnetic field
3. C.Maxwell's screw rule states that if a corkscrew moves in the direction of the current, the hand turns in the direction of the lines of force
4. D.Electromagnets are used in electric bells and telephone receivers.
5. E.The lines of force round a straight current carrying conductor are circular.

A transformer has a primary coil with 500 turns and a secondary coil with 2500 turns. When the voltage input to the primary coil is 120 V, the output is

1. A.6000 V
2. B.600 V
3. C.240 V
4. D.60 V
5. E.24 V

Which of the following statements about electrolysis is NOT correct?

1. A.The substances in solution in the electrolyte become ionized
2. B.Ions are electrically charged and are attracted towards electrodes when a potential difference is applied
3. C.Ions may be discharged at the electrodes, forming bubbles or deposits.
4. D.The mass deposited depends upon the length of time for which current flows
5. E.The mass of gas set free or metal deposited is proportional to the square of the current.

Which of the following statements is NOT correct?

1. A.The average range of distinct vision for a normal eye is from the far distance (infinity) up to about 25 cm in front of the eye
2. B.Longsighted people have difficulty in making the eye lens sufficiently powerful to focus on nearby objects.
3. C.Shortsighted people cannot accommodate distant objects
4. D.Longsighted people need diverging spectacle lenses
5. E.A person with long sight has his eye-ball too short and the image of an object is therefore formed behind the retina.

Which of the following features is NOT a characteristic of natural radioactivity?

1. A.Radioactivity is a nuclear phenomenon
2. B.Radioactivity is exhibited only by elements of mass number greater than 206
3. C.The radioactivity of an element is affected by electric and magnetic fields in the surroundings.
4. D.Radioactive substances emit three types of radiations, α-rays, β-rays and γ-rays
5. E.The radioactive element is transformed into a new element.

What is the number of neutrons in the Uranium isotope ²³⁸₉₂X?

1. A.92
2. B.146
3. C.238
4. D.330
5. E.119