Which of the following is not a suitable method for reducing loss of heat from a piece of hot iron?
AWrapping it in cotton wool
Bpainting it black
CPlacing it in a vacuum
DPlacing it on rubber supports
EKeeping it in a closed wooden box
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Question 22
waec1990
Heat transfer by convection in a liquid is due to the
Atranslatory motion of the molecules of the liquid
Bincreased vibration of the molecules of the liquid about their mean positions
Cexpansion of the liquid as it is heated
Dlatent heat of vaporization of the liquid
Eability of the liquid to evaporate at all temperatures
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Question 23
waec1990
How much heat is given out when a piece of iron of mass 50g and specific heat capacity 460 Jkg-1k-1 cools from 85oC to 25oC?
A1.38 x 106 J
B2.53x104J
C7.66x103J
D1.38x103J
E1.27 X103J
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Question 24
waec1990
lf the temperature of a small quantity of water in a closed container is gradually increased from 0o to 40oC then the density of the water within this range
Aincreases for a while and then decreases
Bdecreases for a while and then increases
Cincreases gradually
Ddecreases gradually
Eremains the same
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Question 25
waec1990
Two solids P and Q of equal mass are heated to the same temperature and dropped simultaneously into two identical containers X and Y containing equal volumes of water at room temperature. The temperature of X will rise higher than that of Y only if the
Avolume of P is greater than that of Q
Bspecific heat capacity of P is higher than that of Q
Cdensity of P is greater than that of Q
Ddensity of P is lower than that of Q
Especitic heat capacity of P is lower than that of Q.
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Question 26
waec1990
Dry hydrogen is trapped by pellet of mercury in a uniform capillary tube closed at one end. If the length of the column of hydrogen at 27°C is 1.0m, at what temperature will the length be 1.20m?
A22.5oC
B32.4oC
C77.0oC
D87.0oC
E360.0oC
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Question 27
waec1990
A cube made of a metal of linear expansivity is warmed through a temperature of t. lf the initial volume of the cube is V what is the increase in volume of the cube?
A1/3α Vt
B1/2α Vt
Cα Vt
D2α Vt
E3α Vt
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Question 28
waec1990
The absolute zero temperature is defined as the temperature at which
Athermal motion ceases
Bthe temperature of a gas is 273oC
Cice melts
Dthe volume of a real gas is maximum
Ethe pressure of a real gas is maximum
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Question 29
waec1990
An object weighs 10.0 N in air and 7.0 N in water. What is its weight when immersed in a liquid of relative density 1.5?
A4.50N
B4.67N
C5.50N
D6.67N
E8.50N
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Question 30
waec1990
The body P shown in the diagram above is in equilibrium. If the mass Q of the body is 10kg, calculate the tension T in the string. (Take g = 10ms2)
A20/√3N
B20N
C50N
D200√3N
E200N
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Question 31
waec1990
A simple pendulum makes 50 oscillations in one minute. What is its period of oscillation?
A0.02s
B0.20s
C0.83s
D1.20s
E50.00s
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Question 32
waec1990
An object R leaves a platform XY with a horizontal velocity of 7m-1 and lands at Q. lf it takes the same object 0.3s to fall freely from Y to P, calculate the distance PQ.(Take g = 1Oms2)
A7.30m
B2.55m
C2.10m
D1.65m
E0.45m.
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Question 33
waec1990
A force F is applied to a body P as shown in the diagram above. If the body P moves through a distance r, which of the following represents the work done?
AFx
BFcosθ/x
CFx tanθ
DFx sinθ
EFx cosθ
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Question 34
waec1990
Two forces each of 4 N act on the opposite sides of a rectangular plate as shown in the diagram above. Calculate the magnitude of g the couple acting on the plate.
A6.4 Nm
B3.2 Nm
C1.6 Nm
D0.8 Nm
E0.0 Nm
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Question 35
waec1990
A girl whose mass is 55kg stands on a spring - weighing machine inside a lift. When the lift starts to ascend, its acceleration is 2ms1. What will be the reading on the machine? (Take g = ms-2)
A66 kg
B55 kg
C44 kg
D22 kg
E11 kg
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Question 36
waec1990
The diagram above represents a portion of a micrometer screw 20 gauge. What is its reading?
A3.70mm
B3.67mm
C3.50mm
D3.33mm
E3.17mm
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Question 37
waec1990
A plane inclined at an angle at 30o to the horizontal has an efficiency of 50%. The force parallel to the plane required to push a load of 120 N uniformly up the plane is
A40√3N
B60N
C120N
D200N
E240N
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Question 38
waec1990
Which of the following are contact forces? I. Force of tension II. Force of fiction, III. Magnetic force III Force of reaction.
AI,II and III only
BI, II and IV only
CI, III and IV only
DII, III and IV only
El and IV only.
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Question 39
waec1990
An oscillating pendulum has a velocity of 2ms-1 at the equilibrium position O and velocity at same point P. Using the diagram above, calculate the height of P above O. (Take g = 10ms2)
A5.0m
B2.0m
C0.4m
D0.2m
E0.1m
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Question 40
waec1990
A particle of mass 2.5 x 10-6kg revolving around the earth has a radial acceleration of 4 X 107 ms-2. What is the centripetal force of the particles?
