JAMB - Physics (1990)

1
Which of the following is a fundamental unit?
Menjawab
(D)
Second
2
A car moving with a speed of 90kmh\(^{-1}\) was brought uniformly to rest by the application of the brakes in 10s. How far did the car travel after the brakes were applied?
Menjawab
(A)
125m
3
A particle of mass M which is at rest splits up into two. If the mass and velocity of one of the particles are m and v respectively, calculate the velocity of the second particle
Menjawab
(D)
\(\frac{mv}{M - m}\)
4
Which of the following statements are correct about an object in equilibrium under parallel forces? i. the total clockwise moments of the forces about any point equals the total anti-clockwise moments about the same point. ii. the total forces in one direction equals the total forces in the opposite direction. iii. the resolved components along the x-axis equals the resolved components along the y-axis.
Menjawab
(A)
i and ii only
5
To keep a vehicle moving at a constant speed v, requires power P, from the engine. The force provided by the engine is
Menjawab
(A)
\(\frac{p}{v}\)
6
A stone of mass m kg is held h meters above the floor for 50s. The work done in joules over this period is
Menjawab
(D)
O
7
A body of mass 10kg rests on a rough inclined plane whose angle of tilt \(\theta\) is variable. \(\theta\) is gradually increased until the body starts to slide down the plane at 30^o. The coefficient of limiting friction between the body and the plane
Menjawab
(C)
0.58
8
An inclined plane which makes an angle of 30^o with the horizontal has a velocity ratio of
Menjawab
(A)
2
9
What is the length of liquid column in a barometer tube that would support an atmospheric pressure of 102000Nm^-2 if the density of the liquid is 2600kgm^-3? [g = 10ms^-2]
Menjawab
(C)
3.92m
10
40m³ of liquid is mixed with 60m³ of another liquid Q. If the density of P and Q are 1.00kgm^-3 and 1.6kgm^-3 respectively, what is the density of the mixture?
Menjawab
(D)
1.36kgm^-3
11
The resistances of platinum wire at the ice and steam points are 0.75 ohm and 1.05 ohm respectively. Determine the temperature at which the resistance of the wire is 0.90 ohm
Menjawab
(B)
50.0^oC
12
A bar of initial length /₀ is heated through a temperature change \(\Delta\)t to a new length I. The linear expansivity, a, of the bar is
Menjawab
(B)
\(\frac{/ - /_o}{/_o \Delta t}\)
13
The pressure of a gas when cooled at constant volume will decrease because the molecules
Menjawab
(A)
collide less frequently with the walls of the container
14
1kg of copper is transferred quickly from boiling water to a block of ice. Calculate the mass of ice melted, neglecting heat loss. [specific heat capacity of copper 400Jkg^-1K^-1 and latent heat of fusion of ice 333 x 10³Jkg^-1]
Menjawab
(C)
120g
15
Which of the following conditions will make water boil at a temperature of 100^oC when the atmospheric pressure is 750mmHg?
Menjawab
(A)
increase the external pressure
16
Which of the following statements are correct? i. land and sea breezes are natural convection currents. ii. convection may occur in liquids or gasses but not in solids. iii. the vacuum in a thermos flask prevents heat loss due to convection only.
Menjawab
(A)
i and ii only
17
A light wave of frequency 5 x 10\(^{14}\)Hz moves through water which has a refractive index of \(\frac{4}{3}\). Calculate the wavelength in water if the velocity of light in air is 3 x 10\(^8\)ms\(^{-1}\)
Menjawab
(A)
4.5 x 10^-7m
18
A wave disturbance travelling in air enters a medium in which its velocity is less than that in air. Which of the following statements is true about the wave medium?
Menjawab
(C)
the frequency of the wave is unaltered while the wavelength is decreased
19
Shadows and eclipses result from the
Menjawab
(B)
rectilinear propagation of light
20
An object which is 3cm high is placed vertically 10cm in front of a concave mirror. If this object produces an image 40cm from the mirror, the height of the image is
Menjawab
(D)
12.00cm
21
A boy looks at the image of an object in a plane mirror. He observes two images, a main bright one and the other faint. The observed images result from?
Menjawab
(A)
reflection only
22
What must be the distance between an object and a converging lens of focal length 20cm to produce an erect image two times the object height?
Menjawab
(C)
10cm
23
For a short sighted person, light rays from a point on a very distant object is focused
Menjawab
(A)
in front of the retina
24
When light is incident on an object which is magenta in colour, which of the following colour would be absorbed?
Menjawab
(B)
Green only
25
In a resonance tube experiment, the effective length of the air column for the first resonance is 20cm when set into vibration by a tuning fork of frequency 480Hz. Neglecting and effect, the velocity of sound in air is
Menjawab
(D)
384ms^-1
26
An organic pipe closed at one end is 80cm long. Determine the frequency of the fundamental note assuming that the speed of sound in air is 340ms-1
Menjawab
(A)
106Hz
27
A sonometer wire of length 100cm under a tension of 10N, has a frequency of 250Hz. Keeping the length of the wire constant, the tension is adjusted to produce a new frequency of 350Hz. The new tension is
Menjawab
(D)
19.6N
28
One of the properties of the earth's magnetic field is that the
Menjawab
(C)
earth's magnetic flux is entirely horizontal at a place where the magnetic dip is zero
29
Which of the following statements are true of an insulated charged body carrying positive charge? i. it contains excess positive charges. ii. it creates an electric field. iii. it possesses potential energy. iv. it carries electric current.
Menjawab
(C)
i, ii, iii only
30
Which of the following is a vector?
Menjawab
(B)
Electric field
31
Three cells each of e.m.f. 1.5v and an internal resistance of 1.0\(\Omega\) are connected in parallel across a load resistance of 2.67\(\Omega\). Calculate the current in the load?
Menjawab
(C)
0.50A
32
When a known standard resistor of 2\(\Omega\) is connected to the 0.0cm end of a meter bridge, the balance point is found to be at 55.0cm. What is the value of the unknown resistor?
Menjawab
(B)
1.64\(\Omega\)
33
The total energy required to send a unit positive charge round a complete electrical circuit is the
Menjawab
(C)
electromotive force
34
Which of the following is an essential physical property of the wires used for making fuses?
Menjawab
(D)
low melting point
35
Which of the following is most suitable for protecting the circuit of 2000W electric iron connected to a 250V mains?
Menjawab
(B)
8A
36
Electrical power is transmitted at a high voltage rather than low voltage because the amount of energy loss is reduced due to
Menjawab
(A)
heat dissipation
37
A lamp is rated 240V, 60W. The resistance of the filament is
Menjawab
(A)
960\(\Omega\)
38
A 0 - 10mA galvanometer with a coil resistance of 30\(\Omega\) can be converted to a 0 - 10A ammeter by using
Menjawab
(B)
0.03\(\Omega\) shunt resistor
39
The number of neutrons contained in the nucleus \(^{238}_{92}U\) is
Menjawab
(B)
146
40
What precaution should a manufacturer take to ensure that energy loss in a transformer is minimized?
Menjawab
(B)
the core should be made of thin sheets of metal
41
A substance has a half of 3mins. after 6mins. the count rate was observed to be 400. What was its count rate at zero time?
Menjawab
(C)
1600
42
The photocell works on the principle of the
Menjawab
(B)
emision of electrons by incident radiation
43
What is the reading of the vernier scale above
Menjawab
(A)
1.88cm
44
Two horizontal forces, 10N and 8N and another force F1 inclined at 30 to the vertical acting as shown in the diagram above, keep the body P in equilibrium, The weight of the body is
Menjawab
(D)
2V3N
45
What is the average velocity of the sprinter whose velocity time graph is as shown above
Menjawab
(C)
8.5ms^-1