JAMB - Physics (1987)

1
Which of the following units is equivalent to kgms^-1?
Απάντηση
(C)
Ns
2
A jet engine develops a thrust of 270Ns when the velocity of the exhaust gases relative to the engine is 300ms^-1. What is the mass of the material ejected per second?
Απάντηση
(C)
0.90kg
3
A man walks 8km north and then 5km in a direction 60^o east of north. Find the distance from his starting point
Απάντηση
(A)
11.36km
4
An elevator of mass 4800kg is supported by a cable which can safely withstand a maximum tension of 60 000N. The maximum upward acceleration the elevator can have is
Απάντηση
(A)
2.5ms^-2
5
A constant force of 40N acting on a body initially at rest gives an acceleration of 0.1ms^-2 for 4s. Calculate the work done by the force
Απάντηση
(C)
32J
6
A body rolls down a slope from a height of 100m. its velocity at the foot of the slope is 20ms^-1. What percentage of its initial potential energy is converted into kinetic energy? [g = 10ms^-1]
Απάντηση
(C)
20%
7
The coefficient of static friction between a 40kg 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 45o to the horizontal. [G = 10ms-1]
Απάντηση
(D)
212N
8
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 behavior is due to
Απάντηση
(C)
surface tension
9
The mechanical advantage(MA) of an inclined plane depends on
Απάντηση
(D)
the ratio of its length to its height
10
A load of 5N gives an extension of 0.56cm in a wire which obeys Hooke's law. What is the extension caused by a load of 20N?
Απάντηση
(C)
2.24cm
11
A cube of side 10cm and mass 0.5kg floats in a liquid with only \(\frac{1}{5}\) of its height above the liquid surface. What is the relative density of the liquid?
Απάντηση
(C)
0.625
12
The distance between the fixed points of a centigrade thermometer is 20cm. What is the temperature when the mercury level is 4.5cm above the lower mark?
Απάντηση
(A)
22.5^oC
13
The length of a side of a metallic cube at 20oC is 5.0cm. Given that the linear expansivity of the metal is 4.0 x 10-5k-1, find the volume of the cube at 120oC .
Απάντηση
(A)
126.50cm³
14
As a result of air at the top of a barometer, the height of the mercury column is 73.5cm when it should be 75.0cm; the volume of the space above the mercury is 8.0cm3. Calculate the correct barometer height when the barometer reads 74.0cm and the volume of the space above the mercury is 6.0cm3.
Απάντηση
(D)
76.0cm
15
Hot water is added to three times its mass of water at 10oC and the resultant temperature is 20oC. What is the initial temperature of the hot water?
Απάντηση
(C)
50^oC
16
22,000J of heat is required to raise the temperature of 1.5kg of paraffin from 20^oC to 30^oC. Calculate the specific heat capacity of paraffin.
Απάντηση
(A)
1466Jkg^-1 ^oC^-1
17
In which of the following are the substance arranged in descending order of their thermal conductivities?
Απάντηση
(A)
copper, steel, glass
18
The vacuum in a thermos flask helps to reduce heat transfer by?
Απάντηση
(B)
convection and conduction
19
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 ?
Απάντηση
(D)
reflection
20
Calculate the amount of heat required to convert 2kg of ice at 2^oC to water at 0^oC. [specific heat capacity of ice = 2090Jkg^-1 ^oC^-1, specific latent heat of fusion of ice = 333kJkg^-1]
Απάντηση
(D)
674 360J
21
A wave has a frequency of 2Hz and a wavelength of 30cm. The velocity of the wave is
Απάντηση
(D)
0.6ms^-1
22
A boat at anchor is rocked by waves whose crest are 100m apart and whose velocity is 25ms^-1. At what interval does the wave crest reach the boat?
Απάντηση
(C)
4.00s
23
Which of the following instruments has a pure tone?
Απάντηση
(C)
tuning fork
24
The lowest note emitted by a stretched string has a frequency of 40Hz. How many overtones are there between 40Hz and 150Hz?
Απάντηση
(B)
2
25
Which of the following statements supports the assumption that light travels in straight lines?
Απάντηση
(B)
a source of light produces distinct shadows of opaque objects
26
When the length I of a piece of wire under constant tension is varied, the relationship of the frequency of the vibration f\(\alpha\)/ is
Απάντηση
(D)
f\(\alpha \frac{1}{1}\)
27
If an object is placed in front of two mirrors inclined at 90o, how many images will be formed?
Απάντηση
(C)
three
28
An object 3.0cm high is placed 60.0cm from a converging lens whose focal length is 20.0cm. Calculate the size of the image formed
Απάντηση
(B)
1.5cm
29
A pool of water appears to be 1.0m deep when viewed vertically from above. If the refractive index of water is 1.33, what is the actual depth of the pool?
Απάντηση
(C)
1.330m
30
A ray of light is incident at an angle of 30o 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?
Απάντηση
(D)
0^o
31
Four lenses are being considered for use as a microscope objective. Which of the following focal lengths is most suitable?
Απάντηση
(B)
+5mm
32
If the angle of declination in a place is 10oE, calculate the true geographic bearing if the compass reads N40oE
Απάντηση
(A)
N50^oE
33
Two capacitance of 6\(\mu\)F and 8\(\mu\)F are connected in series. What additional capacitance must be connected in series with this combination to give a total of 3\(\mu\)F
Απάντηση
(C)
24\(\mu\)F
34
When a transformer has more secondary windings than primary windings, it?
Απάντηση
(A)
has a smaller secondary current
35
A current of 0.5A flows through a resistor when connected to a 40-V battery. How much energy is dissipated in 2 minutes?
Απάντηση
(C)
2400J
36
The direction of the magnetic field at a point in the vicinity of a bar magnet is
Απάντηση
(D)
in the direction the north pole of a compass needle would point
37
When two parallel wires carry currents in opposite directions, the force on either wire is
Απάντηση
(A)
away from the other wire
38
A galvanometer of resistance 20\(\Omega\) is to be provided with a shunt that \(\frac{1}{10}\) of the whole current in a circuit passes through the galvanometer. The resistance of the shunt is
Απάντηση
(B)
2.22\(\Omega\)
39
What type of reaction is represented by the following scheme? \( ^2 _1X \) + \( ^{2} _{1}Y \) + \( ^{3} _{2}Z \) + \( ^{1} _{0}n \) + energy
Απάντηση
(A)
Fusion reaction
40
Which of the following statements is TRUE of photoelectric effect?
Απάντηση
(C)
the energy of the emitted electron depends on the wavelength of the incident light
41
Isotopes are nuclei which have
Απάντηση
(C)
the same atomic number but different number of neutrons
42
A radioactive sample initially contains N atoms. After three half-lives the number of atoms that have disintegrated is
Απάντηση
(D)
\(\frac{7N}{8}\)
43
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?
Απάντηση
(B)
18.0m
44
the fig above shows two connected bodies of masses M\(_1\) and M\(_2\) in equilibrium under gravity. The tension in the upper string is
Απάντηση
(D)
(m\(_1\)+m\(_2\))g
45
A 50kg block is dropped from a point 10m above as shown in the fig above. if the force constant of the spring is 4.0 x 10\(^4\)Nm-1, find the maximum compression of the spring

[g = 10ms-2]
Απάντηση
(B)
0.50m