JAMB - Physics (2020)

1
A few grains of table salt were put in a cup of cold water, kept at constant temperature and left undistributed. Eventually all the water tested salty. This action is due to?
Svar
(D)
diffusion
2
The force required to make an object of mass m, travelling with velocity v, turn in a circle of radius r is
Svar
(A)
\(\frac{mv^2}{r}\)
3
A machine gun with a mass of 5kg fires a 50g bullet at a speed of 100 ms\(^{-1}\). The recoil speed of the machine gun is
Svar
(C)
1 ms\(^{-1}\)
4
If in a simple pendulum experiment the length of the inextensible string is increased by a factor of four, its period is increased by a factor of?
Svar
(D)
2
5
In what range of temperature is the expansion of water anomalous?
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(C)
0\(^o\)C to +4\(^o\)C
6
Which of the following statements about radioactivity is true?

(i) Alpha particle is positively charged

(ii) Beta particle is negatively charged

(iii) Gamma ray is neutral

(iv) Beta particle has the same mass as helium atom

(v) Gamma ray is charged.
Svar
(B)
i, ii, iii only
7
In the study of Physics, temperature and heat are often confused with each other. Which of the following statements correctly defines these two elements?

Svar
(D)
All of the above
8
The effect of closing the key K in the circuit shown in the figure above would be to?
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(A)
increase the current by 0.4A
9
Which of the following statements on the use of X-rays is incorrect? X-rays are used
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(C)
In detecting fingerprints
10
Natural radioactivity consists of emission?

Svar
(D)
\(\alpha\)-particles and \(\beta\)-rays and \(\gamma\)-rays
11
If a source of solid is moving, a stationary listener will hear a sound of different frequency. This is called?
Svar
(A)
doppler effect
12
Which of the following can be described as high tension transmission?
Svar
(B)
Low current and high voltage
13
What is the cost of running five 50W lamps and four 100W lamps for 10 hours if electrical energy costs 2 Kobo per KWh?
Svar
(D)
N0.13
14
Tha mass of a proton is approximately equal to that of
Svar
(C)
a neutron
15
A transformer has 300 turns of wire in the primary coil and 30 turns in the secondary coil. If the input voltage is 100 volts, the output voltage is
Svar
(B)
10 volts
16
A solid weighs 4.8g in air, 2.8g in water and 3.2g in Kerosine. The ratio of density of the solid to that of the kerosine is
Svar
(D)
3
17
One of the following readings represents the measurement of the length of a metal rod using vernier callipers. Taking the reading accuracy into consideration, the most likely one is
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(A)
5.16cm
18
When a sound wave passes from air into water its
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(B)
speed and wavelength increases but its frequency remains the same
19
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)
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(B)
I and II only
20
Two mirrors of the same length are arranges as show in the diagram. A ray of light NO strikes the system at O and emerges along PQ. The emergent ray has been deviated through
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(D)
180\(^o\)
21
A magnetic needle is suspended first at the earth's north magnetic pole and then at a point on the magnetic equator. The respective angles between the needle and the horizontal are
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(D)
90\(^o\) and 0\(^o\)
22
A hydrometer is an instrument for measuring the
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(B)
relative density of a liquid by the method of flotation
23
Consider the three forces acting at O and in equilibrium as shown in the figure. Which of the following equations is/are CORRECT?

I. P\(_1\) cos \(\theta_1\) = p\(_1\) cos \(\theta_2\)

II. P\(_3\) = P\(_1\) cos \(\theta_4\) + P\(_2 cos_2\)

III. P\(_1 \sin \theta_1 = P_2 \sin \theta_2\)
Svar
(C)
III only
24
The refractive index of a liquid is 1.5. If the velocity of light in vacuum is 3.0 x 10\(^8ms^{-1}\), the velocity of light in the liquid is
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(B)
2.0 x 10\(^8ms^{-1}\)
25
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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(D)
125m
26
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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(C)
I and II only
27
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 optical 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 than a certain critical value

IV. Angle of incidence is lesser than a certain critical value

Svar
(D)
I and III only
28
The linear expansivity of brass is 2 x 10\(^{-5}\) \(^oC^{-1}\). If the volume of piece of brass is 10cm\(^3\) at 0\(^o\)C. What will be its volume at 100\(^o\)C?
Svar
(A)
10.06cm\(^3\)
29
The lower and upper fixed points marked on a Mercury-in-glass thermometer are 210mm apart. The end of the mercury column in the tube is 49mm above the lower fixed point in a room. What is the temperature of the room in degrees Celsius?
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(B)
23.3\(^o\)C
30
Heat is supplied uniformly at the rate of 100W to 1.0 x 10\(^{-2}\)kg of a liquid for 20 seconds. If the temperature of the liquid rises by 5\(^o\)C, then the specific heat capacity of the liquid is
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(C)
4.0 x 10\(^4\)Jkg\(^-1\)K\(^-1\)
31
Two divers G and H are at depths 20m and 40m, respectively below the water surface in a lake. The pressure on G is p\(_1\) while the pressure on H is P\(_2\), If the atmospheric pressure is equivalent to 10m of water, then the value of P\(_2\)/P\(_1\) is?

Svar
(C)
1.67
32
The fiqure above represents a block-and-tackle pulley system on which an effort of W Newtons supports a load of 120.0N. If the efficiency of the machine is 40\(^o\), then the value of W is
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(D)
50.0N
33
In an experiment in which molten naphthalene is allowed to cool, the cooling curve i n the figure was obtained. The temperature 80\(^o\)C is known as the
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(C)
melting point
34
In the figure, the value of R is
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(B)
6\(\Omega\)
35
Which of the following instruments consumes the highest current?

I. Electric iron

II. Television set

III. Torchlight

IV. Immersion heater

250v

220v

6v

110v

1kW

110W

30W

500W

Svar
(C)
III