JAMB Physics 1987 past questions and answers

Which of the following units is equivalent to kg m s⁻¹?

1. A.N s⁻¹
2. B.N m s
3. C.N s
4. D.J s⁻¹

A man walks 8 km north and then 5 km in a direction 60° east of north. Find the distance from his starting point.

1. A.11.36 km
2. B.12.36 km
3. C.13.00 km
4. D.14.36 km

The velocity-time graph above describes the motion of a particle between two points P and Q. What is the distance between P and Q?

1. A.17.0 m
2. B.18.0 m
3. C.22.5 m
4. D.30.0 m

A jet engine develops a thrust of 270 N when the velocity of the exhaust gases relative to the engine is 300 m s⁻¹. What is the mass of the material ejected per second?

1. A.81.00 kg
2. B.9.00 kg
3. C.0.90 kg
4. D.0.09 kg

Figure 1 above shows two connected bodies of masses m₁ and m₂ in equilibrium under gravity. The tension in the upper string is

1. A.(m₁ − m₂)g
2. B.m₁g
3. C.m₂g
4. D.(m₁ + m₂)g.

An elevator of mass 4800 kg is supported by a cable which can safely withstand a maximum tension of 60 000 N. The maximum upward acceleration the elevator can have is [g = 10 m s⁻²]

1. A.2.5 m s⁻²
2. B.5.0 m s⁻²
3. C.7.5 m s⁻²
4. D.10.0 m s⁻²

A 50.0 kg block is dropped on a spring from a point 10 m above (Fig. 2). If the force constant of the spring is 4.0 × 10⁴ N m⁻¹, find the maximum compression of the spring. [g = 10 m s⁻²]

1. A.1.25 m
2. B.0.50 m
3. C.0.25 m
4. D.0.05 m

A constant force of 40 N acting on a body initially at rest gives an acceleration of 0.1 m s⁻² for 4 s. Calculate the work done by the force

1. A.8 J
2. B.10 J
3. C.32 J
4. D.160 J.

A body rolls down a slope from a height of 100 m. Its velocity at the foot of the slope is 20 m s⁻¹. What percentage of its initial potential energy is converted into kinetic energy? [g = 10 m s⁻²]

1. A.40%
2. B.35%
3. C.20%
4. D.15%

Figure 3 above represents the main sequence of energy conversion at Kainji Dam. The efficiency of the system is

1. A.Q₁/Q₂
2. B.E/Q₁
3. C.E/(Q₁ − Q₂)
4. D.E/(Q₁ + Q₂)

The coefficient of static friction between a 40 kg crate and concrete surface is 0.25. Find the magnitude of the minimum force needed to keep the crate stationary on the concrete base inclined at 45° to the horizontal. [g = 10 m s⁻²]

1. A.400 N
2. B.300 N
3. C.283 N
4. D.212 N

If a beaker is filled with water it is observed that the surface of the water is not horizontal at the glass-water interface. This behaviour is due to

1. A.friction
2. B.viscosity
3. C.surface tension
4. D.evaporation

The mechanical advantage (MA) of an inclined plane depends on

1. A.its length
2. B.its height
3. C.the product of its length and height
4. D.the ratio of its length to its height.

A load of 5 N gives an extension of 0.56 cm in a wire which obeys Hooke's law. What is the extension caused by a load of 20 N?

1. A.1.12 cm
2. B.2.14 cm
3. C.2.24 cm
4. D.2.52 cm.

A cube of side 10 cm and mass 0.5 kg floats in a liquid with only 1/5 of its height above the liquid surface. What is the relative density of the liquid?

1. A.0.125
2. B.0.250
3. C.0.625
4. D.2.500.

The distance between the fixed points of a centigrade thermometer is 20 cm. What is the temperature when the mercury level is 4.5 cm above the lower mark?

1. A.22.5°C
2. B.29.0°C
3. C.90.0°C
4. D.100.0°C

A metallic strip of iron and brass was heated. Which of the following diagrams accurately illustrates the shape of the strip after heating?

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

The length of a side of a metallic cube at 20°C is 5.0 cm. Given that the linear expansivity of the metal is 4.0 × 10⁻⁵ K⁻¹, find the volume of the cube at 120°C.

1. A.126.50 cm³
2. B.126.25 cm³
3. C.126.00 cm³
4. D.125.00 cm³.

As a result of air at the top of a barometer, the height of the mercury column is 73.5 cm when it should be 75.0 cm; the volume of the space above the mercury is 8.0 cm³. Calculate the correct barometric height when the barometer reads 74.0 cm and the volume of the space above the mercury is 6.0 cm³.

1. A.72.0 cm
2. B.74.5 cm
3. C.75.1 cm
4. D.76.0 cm.

A fixed quantity of gas is subjected to various pressures P and the corresponding volumes V measured at a constant temperature. Which of the following graphs best represent the results?

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

Hot water is added to three times its mass of water at 10°C and the resulting temperature is 20°C. What is the initial temperature of the hot water?

1. A.100°C
2. B.80°C
3. C.50°C
4. D.40°C

22,000 J of heat is required to raise the temperature of 1.5 kg of paraffin from 20°C to 30°C. Calculate the specific heat capacity of paraffin.

1. A.1466 J kg⁻¹ °C⁻¹
2. B.2933 J kg⁻¹ °C⁻¹
3. C.4400 J kg⁻¹ °C⁻¹
4. D.5866 J kg⁻¹ °C⁻¹

Calculate the amount of heat required to convert 2 kg of ice at −2°C to water at 0°C. (Specific heat capacity of ice = 2090 J kg⁻¹ °C⁻¹, specific latent heat of fusion of ice = 333 kJ kg⁻¹).

1. A.666 J
2. B.8360 J
3. C.666 000 J
4. D.674 360 J.

In which of the following are the substance arranged in descending order of their thermal conductivities?

1. A.copper, steel, glass
2. B.steel, copper, glass
3. C.steel, glass, copper
4. D.copper, glass, steel.

The vacuum in a thermos flask helps to reduce heat transfer by

1. A.convection and radiation
2. B.convection and conduction
3. C.conduction and radiation
4. D.radiation only

Which of the following phenomena explains the fact that a house whose roof is coated with white paint will be cooler in the hot season than one coated with black paint?

1. A.conduction
2. B.convection
3. C.refraction
4. D.reflection

A wave has a frequency of 2 Hz and a wavelength of 30 cm. The velocity of the wave is

1. A.60.0 m s⁻¹
2. B.6.0 m s⁻¹
3. C.1.5 m s⁻¹
4. D.0.6 m s⁻¹.

A boat at anchor is rocked by waves whose crests are 100 m apart and whose velocity is 25 m s⁻¹. At what interval does the wave crests reach the boat?

1. A.2500.00 s
2. B.75.00 s
3. C.4.00 s
4. D.0.25 s.

Which of the following instruments has a pure tone?

1. A.guitar
2. B.vibrating string
3. C.tuning fork
4. D.siren

The lowest note emitted by a stretched string has a frequency of 40 Hz. How many overtones are there between 40 Hz and 150 Hz?

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

When the length l of a piece of wire under constant tension is varied, the relationship of the frequency of vibration f with l is

1. A.f ∝ l
2. B.f ∝ 1/l²
3. C.f ∝ √l
4. D.f ∝ 1/l

Which of the following statements supports the assumption that light travels in straight lines?

1. A.Light can be diffracted
2. B.A source of light produces distinct shadows of opaque objects
3. C.A source of light produces interference patterns on a suitably placed screen
4. D.Light can be reflected.

If an object is placed in front of two mirrors inclined at 90°, how many images will be formed?

1. A.Five
2. B.Four
3. C.Three
4. D.Two.

An object 3.0 cm high is placed 60.0 cm from a converging lens whose focal length is 20.0 cm. Calculate the size of the image formed.

1. A.0.5 cm
2. B.1.5 cm
3. C.2.0 cm
4. D.6.0 cm

A pool of water appears to be 1.0 m deep when viewed vertically from above. If the refractive index of water is 1.33, what is the actual depth of the pool?

1. A.0.750 m
2. B.1.013 m
3. C.1.330 m
4. D.13.3000 m

A ray of light is incident at an angle of 30° on one top surface of a parallel-sided glass block of refractive index 1.5. The ray finally emerges from the lower surface. What is the angular deviation of the emergent ray?

1. A.60°
2. B.39°
3. C.28°
4. D.0°.

Four lenses are being considered for use as a microscope objective. Which of the following focal lengths is most suitable?

1. A.−5 mm
2. B.+5 mm
3. C.−5 cm
4. D.+5 cm.

If the angle of declination in a place is 10°E, calculate the true geographic bearing if the compass reads N40°E.

1. A.N50°E
2. B.N40°E
3. C.N30°E
4. D.N25°E

In Fig. 4 above, a voltage V is applied across the terminals P and Q. The voltage across the 1 Ω resistor is

1. A.V/8
2. B.V/4
3. C.V/3
4. D.V/2

Two capacitances of 6 μF and 8 μF are connected in series. What additional capacitance must be connected in series with this combination to give a total of 3 μF?

1. A.3 μF
2. B.16 μF
3. C.24 μF
4. D.30 μF

In Fig. 5 above, M and N are insulated metal spheres in contact. A negatively charged ebonite rod P is brought near M. When M and N are separated and the rod is taken away, which of the following statements is CORRECT?

1. A.Both M and N have acquired negative charges.
2. B.Both M and N have acquired positive charges
3. C.M has acquired negative charge and N positive charge
4. D.M has acquired positive charge and N negative charge.

When a transformer has more secondary windings than primary windings, it

1. A.has a smaller secondary current
2. B.has a greater power output
3. C.is a step-down transformer
4. D.increases the total energy output.

A current of 0.5 A flows through a resistor when connected to a 40-V battery. How much energy is dissipated in 2 minutes?

1. A.1200 J
2. B.1500 J
3. C.2400 J
4. D.96000 J.

The direction of the magnetic field at a point in the vicinity of a bar magnet is

1. A.always towards the north pole of the magnet
2. B.always away from the south pole of the magnet
3. C.along the line joining the point to the neutral point
4. D.in the direction the north pole of a compass needle would point.

When two parallel wires carry currents in opposite directions, the force on either wire is

1. A.away from the other wire
2. B.zero, because the currents cancel each other
3. C.twice as much as when the currents are in the same direction
4. D.towards the other wire.

A galvanometer of resistance 20 Ω is to be provided with a shunt such that 1/10 of the whole current in a circuit passes through the galvanometer. The resistance of the shunt is

1. A.2.00
2. B.2.22
3. C.18.00
4. D.18.22

What type of reaction is represented by the following scheme? ²₁X + ²₁Y → ³₂Z + ¹₀n + energy

1. A.Fusion reaction
2. B.Fission reaction
3. C.Chain reaction
4. D.Radioactive decay.

Which of the following statements is TRUE of photoelectric effect?

1. A.It cannot occur in liquids
2. B.The energy of the emitted electron is independent of the work function of the surface
3. C.The energy of the emitted electron depends on the wavelength of the incident light
4. D.The greater the intensity of the incident light, the greater the energy of the emitted electron.

Isotopes are nuclei which have

1. A.the same number of neutrons and electrons
2. B.equal number of electrons and protons
3. C.the same atomic number but different number of neutrons
4. D.the same number of total particles.

A radioactive sample initially contains N atoms. After three half-lives the number of atoms that have disintegrated is

1. A.N/8
2. B.3N/8
3. C.5N/8
4. D.7N/8