WAEC - Physics (2012)

1
The derived unit of pressure can be expressed as
Respondre
(B)
kg m^-1s^-2
2
The diagram above illustrates trapped air in a syringe placed in water that is gradually heated. It is observed that the piston rises as the temperature of the water rises. Which of the following statements explains this observation?
Respondre
(B)
molecules of trapped air expands more
3
Which of the following devices is used to determine the relative density of an acid?
Respondre
(B)
hydrometer
4
A block of wood of density 0.6 gcm\(^{-3}\), weighing 3.06N in air, floats freely in a liquid of density 0.9 gcm\(^{-3}\). Calculate volume of the portion immersed (g = 10ms\(^{-2}\))
Respondre
(B)
340cm³
5
A metal ball of weight W falls through a column of glycerine of viscosity V. If the ball experiences an upthrust U and terminal velocity is attained, then
Respondre
(B)
W = U + V
6
The movement of fluid up or down a narrow tube is
Respondre
(C)
capillarity
7
Which of the following substances is the most volatile at room temperature?
Respondre
(C)
petrol
8
A bird flies at 10ms\(^{-1}\) for 3s, 15ms\(^{-1}\) for 3s and 20 ms\(^{-1}\) for 4s. Calculate the bird's average speed
Respondre
(C)
15.5 ms^-1
9
The time of flight for a projectile motion is given by the expression
Respondre
(C)
\(\frac{2U sin \theta}{g}\)
10
An object is dropped from the top of a tower. If it takes 4s for it to reach the ground, calculate the height of the tower.(g = 10 ms-2, ignore air resistance)
Respondre
(C)
80m
11
When a body is slightly tilted, it is found that its centre of gravity is slightly raised. What is the state of equilibrium of the body?
Respondre
(B)
stable
12
A simple pendulum makes 50 oscillations in one minute. Determine its period of oscillation
Respondre
(C)
1.20s
13
The tendency for a stationary body to continue to remain at rest when a force is applied to it is known as
Respondre
(C)
inertia
14
A resultant force of magnitude 15N acts on a body of mass 250g. Calculate the magnitude of the acceleration
Respondre
(D)
60.00ms^-2
15
A girl stands on a scale in a lift. If the reading on the scale is less than her weight, then the lift is moving
Respondre
(D)
downward with uniform acceleration
16
The S.I unit of heat is
Respondre
(A)
joule
17
A body is pulled through a distance of 500m by a force of 20N. If the power developed is 0.4kW, calculate the time for which the force acts
Respondre
(B)
25.0s
18
A metal sheet of area 100cm\(^2\) was heated through 70°C. Calculate its new area if the linear expansivity of the metal is 0.000017K\(^{-1}\).
Respondre
(C)
100.24cm²
19
The thermopile is a device for detecting
Respondre
(B)
radiant energy
20
In the formation of sea breeze. wind blows from
Respondre
(D)
sea to land
21
A piece of copper of mass 20g at a temperature of 110°C was dropped into a mixture of ice and water at 0°C. If the final steady temperature of the mixture is 0°C . Calculate the amount of ice that melted [Specific heat capacity of copper = 0.4 Jg\(^{-1}\)K\(^{-1}\), specific latent heat of fusion of ice = 330Jg\(^{-1}\)]
Respondre
(D)
2.70g
22
Which of the following factors decreases the rate of evaporation of a liquid?
Respondre
(A)
increase in pressure over the liquid
23
When two waves are superimposed on each other, the following occurrences are possible, except
Respondre
(D)
dispersion
24
Which of the following properties of waves is exclusive to transverse waves?
Respondre
(D)
polarization
25
An object of height 2.5cm is places 20cm from a convex mirror of focal length 10cm. Calculate the height of its image.
Respondre
(A)
2.5 cm
26
A ray of light passes from air to water to glass to air. Given that the refractive index for light passing from air to water is \(\frac{4}{3}\) and air to glass is \(\frac{3}{2}\), calculate the refractive index of glass relative to water
Respondre
(D)
1.13
27
An object is placed at a point X between the focal point F and the optical centre C of a diverging lens. If F is the focal point on the other side of the lens, the image of the object is formed between
Respondre
(B)
X and C
28
An object is placed 10cm from a converging lens of foal length 15cm. Calculate the magnification of the image formed
Respondre
(A)
3.0
29
A telescope is said to be in normal adjustment when the
Respondre
(D)
objective focal point coincides wih that of the eyepiece
30
The sound heard by a person after the reflection of the sound generated by him is called
Respondre
(C)
echo
31
Which of the following sets of coloured light is/are secondary colours i. Red, Blue and green ii. Blue, cyan and magneta iii. Green, Magenta and yellow, IV Yellow, Cyan and Magenta
Respondre
(C)
iv only
32
When two like charges are brought together, the potential energy of the system formed will
Respondre
(A)
increase because work is done against the field
33
Two capacitors, each of capacitance 2\(\mu\)F are connected in parallel. If the p.d across them is 120V, calculate the charge on each capacitor
Respondre
(C)
2.4 x 10^-4C
34
Which of the following properties is an advantage of lead-acid accumulator over an alkaline accumulator?
Respondre
(D)
possesses high e.m.f
35
Six dry cells each of e.m.f. 2.0 and internal resistance of 1.0\(\Omega\) are connected in parallel across a load of 3.0\(\Omega\). Calculate the effective current in the circuit.
Respondre
(A)
0.63A
36

Two similar cells are used to light two similar lamps as illustrated in the diagrams above. In which of the circuit diagrams are the lamps brightest?
Respondre
(B)
Q
37
A 12\(\Omega\) resistor dissipates 8kJ of heat in 20s. Calculate the current through the resistor
Respondre
(A)
5.8A
38
The magnetic relay is a device used for
Respondre
(D)
controlling another circuit carrying larger current
39
the core of a transformer is usually laminated in order to
Respondre
(B)
reduce eddy current
40
Which of the following modes is the most economical method of transmitting electrical power over long distances?
Respondre
(C)
alternating current at high voltage and low current
41
An inductor is connected to a 24V, 50Hz mains supply. If the current through the inductor is 1.5A, calculate the inductance of the inductor (\(\pi = \frac{22}{7}\))
Respondre
(D)
5.1 x 10^-2H
42
In a R-C circuit
Respondre
(C)
V^rms lags I^rms by 90^o
43
An atom in an excited state is one whose
Respondre
(D)
electron have moved to higher energy level
44
A metal with a work function of 3.0ev is irradiated with ultraviolet light of energy 4.0 ev. The kinetic energy of the ejected electron is
Respondre
(A)
1.0eV
45
Which of the following statements about X-rays is correct? X-rays
Respondre
(B)
are produced when a metal target is used to block fast miving electrons