The inside of a vacuum flask is usually coated with silver to reduce heat lost by
Aconvection
Bconduction
Cradiation
Dabsorption
Eevaporation
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Question 732
waec1996
The heating element in an electric kettle is usually located near the bottom of the kettle because
Awater is a good conductor of heat
Bheat can be more quickly radiated to all parts of the water
Cno heat can be lost to the surroundings
Dthe convectional currents which are set up can carry heat to all parts of the water
Ethe molecules of the heating element can carry heat to all parts of the water.
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Question 733
waec1996
What is the difference in the amount of heat given out by 4kg of steam and 4kg of water when both are cooled from 100oC to 80oC? (Specific latent heat of steam = 2.260,000J kg-1) (Specific heat capacity of water =4,200 J kg-1)
A336,000J
B672,000J
C8,704,000J
D9,040,000J
E9,376,000J
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Question 734
waec1996
A 400W immersion heater is used to heat a liquid of mass 0.5kg. lf the temperature of the liquid increases by 2.5oC in one second, calculate the specific heat capacity of the liquid (Neglect heat losses to the surroundings)
A80 Jkg-1K-1
B320Jkg-1K-1
C500Jkg-1K-1
D1200J kg-1K-1
E2000J kg-1K-1.
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Question 735
waec1996
Which of the following statements is not correct?
AHeat energy can be transformed into mechanical energy
BThat total heat content of a body is the sum of the kinetic energies of its molecules
Clf a body is heated, its molecules move faster.
Dlf a body is cooled, molecular movement remains constant.
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Question 736
waec1996
The pressure of a fixed mass of gas is 2.0 x 105Nm-2 at a known temperature. Assuming that the temperature remains constant, what will be the pressure of the gas if its volume is halved?
A1.0x105Nm-2
B2.0X105Nm-2
C3.0x105Nm-2
D4.0 x105Nm-2
E5.0 x105Nm-2
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Question 737
waec1996
The linear expansivity of a metal P is twice that of another metal Q. When these materials are heated through the same temperature change, their increase in length is the same. Calculate the ratio of the original length of P to that of Q.
A1:4
B1:2
C2:1
D4:1
E6:1
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Question 738
waec1996
A platinum-resistance thermometer has a resistance of 5Ω at 0°C and 9Ω at l00°C. Assuming that resistance changes uniformly with temperature, calculate the resistance of the thermometer when the temperature is 45°C.
A13.9 Ω
B8.9 Ω
C6.8 Ω
D3.2 Ω
E1.8 Ω
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Question 739
waec1996
Two simple pendula x and y make 400 and 500 oscillations respectively in equal time. If the period of oscillation of x is 1.5 seconds, what is the period of oscillation of y?
A0.53s
B0.83s
C1.20s
D1.50s
E1.88s.
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Question 740
waec1996
A stationary object of mass 4kg is set in motion by a net force of 5ON. If the object attains is speed of 5ms-1 in time. Calculate the value of t.
A0.20s
B0.40s
C0.63s
D0.80s
E1.30s
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Question 741
waec1996
A body of mass 2kg is suspended from the ceiling of a lift with a light inextensible string. lf the lift moves upwards with acceleration of 2ms-2, calculate the magnitude of the tension in the string (g = 1Oms-2)
A24N
B20N
C16N
D4N
E0N
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Question 742
waec1996
A body of mass 4.2kg moving with velocity 10ms-1 due east, hits a stationary body of mass 2.8kg. If they stick together after collision and move with velocity V due east, calculate the value of V
A3ms-1
B6ms-1
C7ms-1
D15ms-1
E17ms-1
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Question 743
waec1996
The magnitude of the force required to make an object of mass M move with speed V in a circular path of radius R is given by the expression.
Amr/v
B(mr) 2/v
Cmv2/r
Dmv/2
Emv/r
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Question 744
waec1996
Two spanners X and Y of lengths 15cm and 20cm respectively are used in turn to give a screw of pitch 2mm one complete rotation. If Rx and Ry are the respective velocity ratios of the spanners then the ratio Rx : Ry is
A1 : 50
B3 : 20
C3:4
D4:3
E20:3
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Question 745
waec1996
The velocity ratio and efficiency of a system of pulleys are 6 and 80% respectively. How much effort is required to lift a load of mass 120kg with this system? (g=10ms-2)
A25N
B90N
C96N
D250N
E960N
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Question 746
waec1996
A rocket is launched from the surface of the earth. If the radius of the earth is 6.4 x 106m and the acceleration of free fall due to gravity is 1Oms-1 calculate the escape velocity of the rocket.
A2.53 x 104ms-1
B1.13 x 104ms
C8.00 x 103ms-1
D4.23 x 103ms-1
E6.41 x 104ms-1
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Question 747
waec1996
A ball of mass 5.0kg hits a smooth vertical wall normally with a speed of 2ms-1 and rebounds with the same speed. Determine the impulse experienced by the ball
A20.0kg ms-1
B10.0kg ms-1
C5.0kg ms-1
D1.3kg ms-1
E0.0kg ms-1.
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Question 748
waec1996
The diagram above illustrates the velocity-time graph of the motion of a body. Calculate the total distance covered by the body
A50m
B65m
C175m
D225m
E300m
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Question 749
waec1996
A loaded test-tube which floats upright in water is carefully and slightly depressed and then released. Which of the following best describes the sub-sequent motion of the test-tube?
ACircular
BRotational
CRandom
DOscillatory
ETranslational
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Question 750
waec1996
The diagram above represents a portion of a micrometer screw gauge in which the horizontal scale is in millimetres. What is the reading on the instrument?
