JAMB - Physics (1979)

1
The density 400cm³ of palm oil was 0.9gcm^-3 before frying. If the density of the oil was 0.6gm^-3 after frying,assuming no loss of oil due to spilling, its new volume was
Answer
(B)
600cm³
2
Which of the following statements defines correctly the efficiency of a machine?
Answer
(C)
the useful work done by the machine divided by the total work put into the machine
3
A 500kg car which was initially at rest travelled with an acceleration of 5m sec^-2, its kinetic energy after 4 seconds was
Answer
(A)
10⁵J
4
Two closed vessels contain equal volumes of boiling water and are identical except that one is blackened on the outside while the other is polished. Which of the following is correct?
Answer
(E)
the black vessel will cool faster because a black surface radiates heat faster than a polished one
5
The temperature at which the water vapour present in the air saturates the air and begins to condense is known as
Answer
(D)
dew point
6
Which of the following types of waves cannot travel through a vacuum?
Answer
(A)
sound waves
7
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
Answer
(E)
2
8
In what range of temperature is the expansion of water anomalous?
Answer
(E)
0^oC to +4^oC
9
When the vapour of a substance is in equilibrium with its own liquid, it is said to be
Answer
(E)
saturated
10
If the wavelength of a wave travelling with a velocity of 360ms-1 is 60m, the period of the wave is
Answer
(C)
0.17s
11
The heights of the mercury thread in a mercury-in-glass thermometer when in melting ice and then in steam are 3cm and 18cm respectively. At a temperature of 60^oC the height would be
Answer
(D)
12cm
12
An object is placed 30cm from a concave mirror of focal length 15cm. the linear magnification of the image produced is
Answer
(C)
1
13
If a given mass at constant pressure obeys the relation...volume is proportional to the absolute temperature...the gas is said to obey
Answer
(D)
Charles' Law
14
A man standing between two parallel mirrors in a barber's shop will see the following number of his own image
Answer
(E)
infinite
15
Which of the following statements is incorrect? The sensitivity of a galvanometer which incorporates an optical lever arrangement may be increased by providing
Answer
(E)
a light source with a greater intensity
16
A landlord has eight 40W electric light bulbs, four 60W bulbs and two 100W bulb in his house. If he has all the points on for five hours daily and if N.E.P.A. charges 5k per unit, his bill for 30 days is
Answer
(A)
N5.70
17
Which of the following statements is correct? The reading of pressure on a mercury barometer is independent of
Answer
(A)
the cross-sectional area of the tube
18
What are the units of thermal conductivity?
Answer
(B)
Joule sec^-1m^-1k^-1
19
Which of the following statements is correct? The magnetized state of an iron bar can be destroyed completely by
Answer
(A)
heating the bar to a high temperature
20
An electric cell has an internal resistance of 2 ohms. A current of 0.5A is found to flow when a resistor of 5 ohms resistance is connected across it. What is the electromotive force of the cell?
Answer
(B)
3.5 volts
21
Which of the following is the correct definition of 'half-life'?
Answer
(B)
the time it takes a radioactive material to decay to half of its original quantity
22
The bulb of a motorcycle head-lamp is marked 40W, 6V. The resistance of the filament when it is switched on is
Answer
(E)
\(\frac{6^2}{40}\)ohms
23
In an electrolysis experiment, a cathode of mass 5g is found o weigh 5.01g after a current of 5A flows for 50 seconds. What is the electrochemical equivalent of the deposited substance?
Answer
(A)
0.00004g/C
24
Which of the following statements about radioactivity are 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
Answer
(C)
i, ii and iii only
25
Consider a thick glass tumbler and a thin glass tumbler which are made of the same kind of glass. Some hot liquid is poured into them. Which of the following statements is correct?
Answer
(D)
the thick tumbler is more likely to crack because uneven expansion persists for a longer time within the thicker glass
26
A capacitor and a resistor are connected in series with each other and in series with an accumulator of negligible internal resistance. The potential across the terminals of the capacitor is
Answer
(B)
less than the e.m.f by the potential drop across the resistor
27
Which of the following statements is true? The frequency of a vibrating string is
Answer
(E)
proportional to the square root of the tension within it
28
An air bubble rises from the bottom to the top of a water dam which is 40m deep. The volume of the bubble just below the surface is 2.5cm³. Find its volume at the bottom of the dam, if atmospheric pressure is equivalent to 10m water
Answer
(E)
0.5cm³
29
Which of the following electromagnetic waves has the shortest wavelength?
Answer
(B)
X-rays
30
All the heat generated in a 5 ohms resistor by 2A flowing for 30 seconds is used to evaporate 5g of a liquid at its boiling point. Which of the following is the correct value of the specific latent heat of the liquid?
Answer
(C)
120Jg^-1
31
The speed of light in air is 3 x 10⁸ms^-1. If the refractive index of light from air-to-water is \(\frac{4}{3}\), then which of the following is the correct value of the speed of light in water?
Answer
(B)
2.25 x 10⁸ms^-1
32
On which of the following is the operation of a moving coil galvanometer based?
Answer
(D)
Force on current carrying conductor in a magnetic field
33
A body is released from rest and allowed to fall freely from a given height under gravity. The kinetic energy at its half-way point is?
Answer
(C)
a half of its initial energy
34
It is known that a neutron exists in a light atomic nucleus. Which of the following also exists in the nucleus?
Answer
(D)
a proton
35
A weight of 1000 grams hangs from a lever 20cm to the fulcrum. At the left is a 500-gram weight 20cm from the fulcrum, and a 200-gram weight x cm away from the fulcrum. What is the value of x that will make the lever balanced?
Answer
(A)
50cm
36
Radio carrier waves are generated by causing electrons to oscillate rapidly in
Answer
(E)
a transmitter
37
Which of the following statements is correct? Silvered walls of a vacuum flask are used to prevent
Answer
(D)
heat loss due to radiation
38
A concave lens of focal length 20cm form an image 1/2 the size of the object. The object distance is
Answer
(C)
60cm
39
The diagram shows lens arrangement in
Answer
(B)
astronomical telescope
40
In a given circuit, the cell P has an emf 1.5V and an unknown internal resistance while cell Q has an emf 2.0V and an internal resistance of 1 ohm if the ammeter reads 50m A, Then r is equal to
Answer
(D)
2.0 ohm
41
An air column 10cm in length is trapped into the sea end of a capillary tube by a 15cm column of mercury with the tube held vertically as shown above. On inverting the tube the air column becomes 15cm long. The atmospheric pressure during the experiment is
Answer
(C)
75cm
42
In a resonance tube experiment, which is illustrated above, the velocity of sound in air is 327.68m/s, the frequency of the turning fork used is therefore?
Answer
(C)
512HZ
43
A uniform bean HK of length 10m and weighing 200N is supported at both ends as shown above. A man weighing 1000N stands at a point P on the beam. If the reactions at point H an K respectively are 800N and 400N, Then the distance HP is
Answer
(C)
3m
44
Fig 8 shows a current I flowing in a copper wire situated in a magnetic field existing between the pole-pieces of a horse-shoe magnet.
Which of the following statements is correct?
Answer
(B)
The wire will experience a force in the direction out of the paper
45
For the wave motion represented above

The wavelength is given by
Answer
(D)
s