JAMB UTME - Physics - 1988

Two forces whose resultant is 100N, are at right angle to each other. If one of them makes an angle 30o with the resultant, determine its magnitude.

Détails de la réponse

COS 30o = $\frac{F_1}{100}$

F1 = 86.6N

When heat is applied to one end of a metal rod, the molecules at the other end soon begin to vibrate with greater amplitude than before because heat has been transferred by

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The speed of sound in air at sea-level is 340ms-1 while that of light is 300 000kms-1. How far (to the nearest meter) from the center of a thunderstorm is an observer who hears a thunder 2s after a lightening flash?

Détails de la réponse

Distance = 340 x 2 = 680ms-1

To obtain a magnification of 2.5, how far should an object be placed from the pole of a thin converging lens of focal length 10.20m?

Détails de la réponse

v = 2.5u

F = $\frac{uv}{u+v}$

0.2 = $\frac{u\times 2.5u}{u+2.5u}$

u = 0.28m

The wire X in the figure above is at right angles to the plane of the paper and carries a current into the paper. at which of the points labelled 1-4, will the magnetic flux density due to this current be in the same direction as that of the horizontal component of earth's magnetic field

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A piano wire 0.5m long has a total mass of 0.01kg and is stretched with a tension of 800N. Calculate the frequency of the wire when it sounds its fundamental note

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F = $\frac{1}{2L}$$\sqrt{\frac{T}{m}}$

N:B m is mass per length

= $\frac{0.01}{0.5}$

= 0.02kgm-1

F = $\frac{1}{2\times 0.5}$$\sqrt{\frac{800}{0.02}}$

= 200Hz

The product PV where P is pressure and V is volume has the same unit as

Détails de la réponse

PV = $\frac{N}{m^2}$ x $\frac{m^2}{1}$

= Nm

A household refrigerator is rated 200 watts. If electricity costs 5k per kWh, what is the cost of operating it in 20 days?

Détails de la réponse

Energy(kWhr) = 200 x 10-3 x 20 x 24

= 96kwhr

1 kwhr cost 5 kobo ; 96 kwhr will cost

5 x 96 = 480 kobo

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$\frac{\text{speed of driver}}{\text{speeder driven}}$ = $\frac{\text{no. of teeth of driver}}{\text{no. of teeth of driven}}$

$\frac{120}{V}$ = $\frac{20}{60}$

v = 360 rev s-1

A note is called an octave of another note when

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A particle is injected perpendicularly into an electric field, it travels along a curved path as depicted in the image above,the particle is

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The amount of heat needed to raise the temperature of 10kg of copper by 1k is its

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Which of the following are the correct SI units of the quantities indicated? i.N(Force) II. Mn-1 (Torque) iii. watt(Power) iv. kgms-2

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A spectrum of sunlight is said to be impure when

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Which of the following ammeters may be used to measure alternating currents? i. moving-coil ammeter ii. moving-iron ammeter iii. hot-wire ammeter

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E, F and G are yellow, red and cyan transparent light filters respectively. The color of a white opaque object when viewed through the arrangement of the filters above is

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Which of the following factors affects the speed of sound in air? i. Temperature ii. pressure iii. Frequency

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When a resistance R is across a cell, the voltage across the terminals of the cell is reduced to two-third of its normal value. The internal resistance of the cell is

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IR = $\frac{2}{3}$ I(R + r)

r = $\frac{1}{2}$R

The principle of operation of an induction coil is based on

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How long will it take a 60kg man to climb a height of 22m if he expended energy at a rate of 0.25kW. [g = ms-2]

Détails de la réponse

power = mgh

0.25 x 103 = $\frac{60\times 10\times 22}{t}$

t = 52.8 sec

A force, 10N, drags a mass 10kg on a horizontal table with an acceleration of 0.2ms. If the acceleration due to gravity is 10ms-1, the coefficient of friction between the moving mass and the table is

Détails de la réponse

$\mu$mg = ma

$\mu$ x 10 x 10 = 10 x 0.2

$\mu$ = 0.02

The figure above shows two waveforms X and Y. If the frequency of X is 30Hz what is the frequency of Y

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A slight loading of a tuning fork has the effect of

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In the figure above, what is the angle of reflection of the ray of light at mirror M?

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Two strings of the same length and under the same tension gives notes of frequencies in the ratio 4 : 1. The masses of the strings are in the corresponding

Détails de la réponse

F = $\frac{1}{2L}$$\sqrt{\frac{T}{m}}$

$\frac{F_1}{F_2}$ = $\sqrt{\frac{m_2}{m_1}}$

$\frac{1}{4}$ = $\sqrt{\frac{m_2}{m_1}}$

$\sqrt{\frac{m_2}{m_1}}$ = $\frac{1}{2}$

A particle starts from rest and moves with a constant acceleration of 0.5ms-2. The distance covered by the particle in 10s is

Détails de la réponse

X = ut + $\frac{1}{2}$at

= (0 x 10) + ($\frac{1}{2}$ x 0.05 x 10 x 10)

= 25m

A dynamo primarily combines

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Which of the following media allow the transmission of sound wave through them i. Air. ii. Liquids. iii. Solids.

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When white light is dispersed by a spectrometer, the component having the shortest wavelength is

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Which of the following properties is/are common to all waves? i. Diffraction ii. Refraction iii. Interference

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Which of the following quantities are scalars? i. Electrical potential ii. Torque iii. Momentum iv. Kinetic energy

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In a certain fusion reaction, a deuteron (${}_1^{2}H$) interacts with a triton (${}_1^{3}He$) and produces an a-particle (${}_2^{4}He$) and a second product. The second product is

Détails de la réponse

${}_1^{2}H$ + ${}_1^{3}H$ $\to$ ${}_2^{4}He$ + ${}_0^{1}He$

A body whose mass is 2kg and has a volume of 500cm just floats when completely immersed in a liquid. Calculate the density of the liquid

Détails de la réponse

since the object floats, density of liquid = density of object

D = $\frac{m}{v}$

= $\frac{2}{500\times 10}$

= 4.0 x 103kgm-3

Which of the following statement is TRUE of ultraviolet, visible and infra-red rays?

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The figure above shows three different ways of hanging a heavy picture from a hook. the tension in the string will be

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Which of the following symbolic representations is correct for an atom X with 22 electrons and 43 neutrons?

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A tap supplies water at 25oC while another supplies water at 75oC. If a man wishes to bathe with water at 40oC, the ratio of the mass of cold water to the mass of hot water required is

Détails de la réponse

Heat lost = heat gained

mh x c x (75 - 40) = mc x c x (40 - 25)

$\frac{m_h}{m_c}$ = $\frac{35}{15}$

= $\frac{7}{3}$

In the circuit diagram above, the ammeter reads a current of 3A when R is 5 ohms and 6A when R is 6 ohms,the value of the unknown resistance X is

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A cell of internal resistance 2 ohms supplies current to a 6 ohms resistor. The efficiency of the cell is

Détails de la réponse

Efficiency = $\frac{IR}{I(R+r)}$ x 100

= $\frac{6}{I(2+6)}$ x 100

= 75%

An object is placed 10cm in front of a concave mirror of focal length 15cm. What is the position and nature of the image formed?

Détails de la réponse

F = $\frac{uv}{u+v}$

15 = $\frac{10\times v}{10+v}$

v = -30cm

A lorry travels 10km northwards, 4km eastwards, 6km southwards, 4km westwards to arrive at a point T. What is the total displacement?

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When taking a penalty kick, a footballer applies a force of 30.0N for a period of 0.05s. if the mass of the ball is 0.075kg, calculate the speed with which the ball moves off.

Détails de la réponse

F = $\frac{m(v-u)}{T}$

30 = $\frac{0.75(v-0)}{0.05}$

v = 20ms-1

The figure above shows displacement-time graphs for three different motions. which of the following statements is correct

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Which of the following phenomena explains the formation of a mirage? i. Reflection ii. Refraction iii. Diffraction

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When one arm of a U-tube manometer is connected to a gas supply, the levels of mercury in the two arms of the U-tube is shown in the figure above, if the atmospheric pressure is 76.0cm hg, the gas pressure is

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