JAMB UTME - Physics - 1983

The total length of a spring when a mass of 20g is hung from its end is 14cm, while its total length is 16cm when a mass of 30g is hung from the same end. Calculate the unstretched length of the spring assuming Hooke's law is obeyed.

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Let unstretched length = L

e1 = 14 - L and e2 = 16 - L

Using, $\frac{m_1}{e_1}$ = $\frac{m_2}{e_2}$

$\frac{20}{14-L}$ = $\frac{30}{16-L}$

L = 10cm

An electric current of 3Aflowing through an electric heating elements of resistance 20 embedded in 1,000g of an oil raises the temperature of the oil by 10oC in 10 seconds then the specific heat capacity of the oil is

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Heat energy = Electrical energy

mc$\Omega$ = I2RTt

1000 x c x 10 = 3 x 3 x 20 x 10

0.18Jg-1oC

If the force of a charge of 0.2 coulomb in an electric field is 4N, then the electric field intensity of the field is

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Field intensity = $\frac{force}{charge}$

$\frac{4}{0.2}$ = 20N/C

which of the following is NOT correct? i. the pitch of a sound note depends on the frequency of vibrations. ii. the intensity of a sound note is proportional to the amplitude of vibrations. iii. beats are produced by two sources of sound because one wave is travelling faster than the other. iv. when two sources of sound of frequencies 500Hz and 502Hz are sounded together, a beat frequency of 2Hz is observed. v. the first harmonic of a tone have double the frequency of the fundamental note.

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The electrochemical equivalent of a metal is 0.126 x 10-6 kgC-1. The mass of the metal that a current of 5A will deposit from a suitable bath in 1 hour is

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m = Itz

= 5 x 3600 x 0.126 x 10-6

= 2.268 x 10-3kg

The image above shows an inverted U-tube with the open end, O of one limb below the level, W of water in the tank, in order that water should begin to flow from the tank it is is necessary that

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In the Figure above, QR is a vertical conductor and the current I flows from R to Q, P is a point on the horizontal plane and is to the south of the wire. The direction of the magnetic field at P due to the current is

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1,000 identical drops of oil of density 500kgm-3 have a total mass of 5 x 10-4kg. One of the drops forms a thin film of area 0.5m2 on water. The thickness of the film is

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Mass of one oil = $\frac{5\times {10}^{-4}}{1000}$

= 5 x 10-4kg

Density = $\frac{\text{mass}}{\text{area x thickness}}$

500 = $\frac{5\times {10}^{-7}}{\text{0.5 x thickness}}$

thickness = 2 x 10-9m

Each of the figures in the diagram above represent two current carrying conductors situated close to each other. In which two diagrams, are the forces between the two wires attractive

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Which of the following arrangements in the sequence shown can be used to obtain a pure spectrum of white light?

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A 24V potential difference is applied across a parallel combination of four 6-ohms resistor, The current in each resistor is

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I = $frac246$

= 4A

Which of the following statements about friction is NOT correct?

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Which of the following may be used to determine the relative humidity in a physics laboratory I. Manometer

II. Wet-and-Dry Bulb Hygrometer

III. Hair Hygrometer

IV. A Hydrometer

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The difference of potential between the terminals of cells is 2.2 volts. When a 4ohm resistor is connected across the terminals of this cells, the potential difference is 2 volts. What is the internal resistance of the cell?

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IR = 2 and Ir = 0.2

I = $\frac{2}{R}$ ; I = $\frac{0.2}{r}$

$\frac{2}{4}$ = $\frac{0.2}{r}$

r = 0.4$\Omega$

Which of the following is NOT a vector quantity?

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Which of the following conditions are necessary and sufficient for total internal reflection to take place at the boundary between two optical media? i. light is passing from optically denser medium to optically less dense medium. ii. light is passing from optically less dense medium to optically denser medium. iii. angle of incidence is greater. iv. angle of incidence is lesser

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In a resonance tube experiment, a tube of fixedlength in closed at one end and several turningforks of increasing frequency used to obtainresonance at the open end. If the turning fork withthe lowest frequency which gave resonance had a frequency f1 and the next turning fork to giveresonance had a frequency f2, find the ratio f2/ f1.

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Ripples on water are similar to light waves in that they both

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The speed of light in vacuum is 3.0 x 108ms-1. If the refractive index of a transparent liquid is $\frac{4}{3}$, then the speed of light in the liquid is

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n = $\frac{\text{speed in air}}{\text{speed in water}}$

$\frac{4}{3}$ = $\frac{3\times {10}^8}{v}$

v = 2.25 x 10 8ms-1

The refractive index of liquid is 1.5. If the velocity of light in vacuum is 3.0 x 108ms-1, the velocity of light in the liquid is

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n = $\frac{\text{speed in air}}{\text{speed in glass}}$

1.5 = $\frac{3\times {10}^4}{\text{speed in glass}}$

speed in glass = 2 x 108ms-1

Which of the following figures gives the correct resultant R of two vectors P and Q?

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The force with which an object is attracted to the earth is called its

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The specific latent heat of vaporization of a substance is always

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In a resonance tube experiment, a tube fixed length is closed at one end and several tuning forks of increasing frequency used to obtain resonance at the open end. If the tuning fork with the lowest frequency which gave resonance had a frequency f1 and the next tuning fork to give resonance had a frequency f2, find the ratio $\frac{f^2}{f^2}$.

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If the pressure on 100cm3 of an ideal gas is doubled while its kelvin temperature is halved, then the new volume of the gas will become

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$\frac{P_1{V}_1}{T_1}$ = $\frac{P_2{V}_2}{T_2}$

P2 = 2P ; T1 = 2T2

therefore, $\frac{P_1\times 1000}{2T_2}$ = $\frac{2P_2\times V_2}{T_2}$

= 25cm

A machine has a velocity ratio of 5. It requires a 50kg weight to overcome a 200kg weight. The efficiency is

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Efficiency = M.A x 100%

= $\frac{200}{50}$ x $\frac{1}{5}$ x 100

= 80%

A train has an initial velocity of 44ms-1 and an acceleration of -4ms-1. Its velocity after 10 seconds is

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Using V = at + u

V = (-4 x 10) + 44

= 4ms-1

Which of the following best describes the energy changes which take place when a steam engine drives a generator which lights a lamp?

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Four resistors R1, R2, R3 and R4 are connected in series as shown above, V1, V2, V3 are voltmeters connected as indicated above. Which of the following relations is correct??

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A ship travelling towards a cliff receives the echo of its whistle after 3.5 seconds. A short while later, it receives the echo after 2.5 seconds. If the speed of sound in air under the prevalling condition is 250ms -1, how much closer is the ship to the cliff?

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Difference in time = 1 sec.

echo time = 1 $÷$ 2 = 0.5 sec.

= 0.5 x 250

= 125m

The range of wavelengths of the visible spectrum is 400nm - 700nm. The wavelength of gamma rays is

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The diagram above shows three circuits, the internal resistances of the batteries are negligible. which of the currents is the largest

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Which of the following may be used to determine relative humidity in a physics laboratory?
I. Manometer
II. Wet-and-dry bulb hygrometer
III. Hair hygrometer
IV. A hydrometer.

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Which of the following statements is true about liquid pressure is NOT correct? The pressure

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Of the following derived units, the one that is not a unit of power is

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Which of the following statements is CORRECT? i. the mass number is equal to the total number of protons and electrons in an atom. ii. the atomic number is equal to the number of protons in an atom. iii. the number of electrons in an atom is equal to the total number of protons and neutrons in the nucleus.

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The linear expansivity of brass is 2 x 10-5oC-1. If the volume of a piece of brass is 10cm3 at 0oC, what will be its volume at 100oC?

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3 x $\alpha$ = $\frac{V_2-V_1}{\Delta \theta \times V_1}$

3 x 2 x 10-5 = $\frac{V_2-10}{10\times 100}$

V2 = 10.06cm3

If the normal atmospheric pressure in a laboratory supports a column of mercury 0.76m high and the relative density of mercury is 13.8, then the height of water column which atmospheric pressure will support in the same laboratory at the same time is

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Density of H2O = 1gcm3

Density x pressure = constant

D1 x P1 = D2 x P2

13.6 x 0.76 = 1 x P2

P2 = 10m

A short response to time is obtained in liquid-in-glass thermometer when the

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If relative density of a metal is 19, what will be the mass of 20cm3 of the metal when immersed in water?

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R.d = 19, therefore, density = 19gcm-3

mass = velocity x density

= 20 x 19

= 380g

A piece of wood is floating on water. The forces acting on the wood are

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Which of the following statements about defects of vision is/are CORRECT? i. for a long sighted person, close objects appear blurred. ii. for a short sighted person, distant objects appear blurred. iii. short sight is corrected by using a pair of converging lenses.

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A milliameter with full scale deflection of 10mA has an internal resistance of 5 ohms. It would be converted to an ammeter with a full scale deflection of 1A by connecting a resistance of

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I = 1 - (10 x 10-3)

= 0.99A

IR = 10 x 10 x 10-3 x 5

R = $\frac{5}{99}$$\Omega$

PQ is a thin rod on a horizontal table, RS is a plane mirror inclined at ${45}^{\circ }C$ to the horizontal as shown above. The image of PQ as seen in the mirror by the eye T is

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Longitudinal waves do not exhibit

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a force of 16N applied 4.0kg block that is at rest on a smooth, horizontal surface. What is the velocity of the block at t = 5 seconds?

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F = ma

= $\frac{m(u-v)}{t}$

16 = $\frac{4(v-0)}{5}$

v = 20ms-1

A man of mass 50kg ascends a flight of stairs 5m high in 5 seconds. If acceleration due to gravity is 10ms-2, the power expended is

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Power = $\frac{\text{force x distance}}{\text{time}}$

= 50 x 10 x 5 = 500W