(i) Short sightedness (myopia)
(ii) Concave lens (diverging lens)
Wilfykil answered the question on March 27, 2019 at 05:19
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On a certain day when the temperature is 370c, the pressure in an open gas jar is 640mm of mercury. The jar is then sealed...
(Solved)
On a certain day when the temperature is 370c, the pressure in an open gas jar is 640mm of mercury. The jar is then sealed and cooled to the temperature of 170c. Calculate the final pressure.
Date posted:
March 27, 2019
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Answers (1)
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In an experiment to determine the specific latent heat of vaporization of water, steam at 1000c was passed into water contained in a well-lagged copper...
(Solved)
In an experiment to determine the specific latent heat of vaporization of water, steam at 1000c was passed into water contained in a well-lagged copper calorimeter. The following measurements were made:
Mass of calorimeter = 50g
Initial mass of water = 70g
Final mass of calorimeter + water + condensed steam = 123g
Final temperature of mixture = 300C
(Specific heat capacity of water = 4200 J kg -1K and specific heat capacity for copper = 390 J kg -1 K-1)
Determine the:
i) Mass of condensed steam
ii) Heat gained by the calorimeter and water
iii) Given that L is the specific latent heat of evaporation of steam
I. Write an expression for the heat given out by steam
II. Determine the value of L.
Date posted:
March 26, 2019
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Answers (1)
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An immersion heater rated 90W is placed in a liquid of mass 2kg. When the heater is switched on for 15 minutes, the temperature of...
(Solved)
An immersion heater rated 90W is placed in a liquid of mass 2kg. When the heater is switched on for 15 minutes, the temperature of the liquid rises from 200C to 300C. Determine the specific heat of the liquid.
Date posted:
March 26, 2019
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Answers (1)
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A pump uses a mixture of petrol and alcohol in the ratio 4: 1 by mass to raise 100kg of water from a well 200m...
(Solved)
A pump uses a mixture of petrol and alcohol in the ratio 4: 1 by mass to raise 100kg of water from a well 200m deep.
i) How much energy is given by 1g of mixture?
ii) If the pump is 40% efficient, what mass of this mixture is needed to raise the water?
Date posted:
March 26, 2019
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Answers (1)
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An energy saving stove when burning steadily has an efficiency of 60%. The stove melts 0.03kg of ice at 00c in 180 seconds. Calculate; -
i)...
(Solved)
An energy saving stove when burning steadily has an efficiency of 60%. The stove melts 0.03kg of ice at 00c in 180 seconds. Calculate; -
i) The power rating of the stove.
ii) The heat energy wasted by the stove.
Date posted:
March 26, 2019
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Answers (1)
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An electric heater rated 6000W is used to heat 1kg of ice initially at -100c until all the mass turns to steam. Given that
(Solved)
An electric heater rated 6000W is used to heat 1kg of ice initially at -100c until all the mass turns to steam. Given that:
Latent heat of fusion =334kJ-1
Specific heat capacity of ice= 2,260J kg -1 K -1
Specific heat capacity of water = 4, 200J kg-1 K-1
Latent heat of vaporization = 2, 260KJ kg -1 K -1
Calculate the minimum time required for this activity.
Date posted:
March 26, 2019
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Answers (1)
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An electric toy is rated 100W, 240V. Calculate the resistance of the toy when operating normally.
(Solved)
An electric toy is rated 100W, 240V. Calculate the resistance of the toy when operating normally.
Date posted:
March 26, 2019
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Answers (1)
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An electrical heater is labelled 120W, 240V. Calculate;
a) The current through the heating element when the heater is on.
b) The resistance of the element used...
(Solved)
An electrical heater is labelled 120W, 240V. Calculate;
a) The current through the heating element when the heater is on.
b) The resistance of the element used in the heater.
Date posted:
March 26, 2019
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Answers (1)
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An electrical appliance is rated as 240V, 200W. What does this information mean?
(Solved)
An electrical appliance is rated as 240V, 200W. What does this information mean?
Date posted:
March 26, 2019
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Answers (1)
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What is power as it relates to electrical energy?
(Solved)
What is power as it relates to electrical energy?
Date posted:
March 26, 2019
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Answers (1)
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How many 100W electric irons could be safely connected to a 240V moving circuit fitted with a 13A fuse?
(Solved)
How many 100W electric irons could be safely connected to a 240V moving circuit fitted with a 13A fuse?
Date posted:
March 26, 2019
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Answers (1)
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When a current of 2A flows in a resistor for 10 minutes, 15KJ of electrical energy is dissipated. Determine the voltage across the resistor.
(Solved)
When a current of 2A flows in a resistor for 10 minutes, 15KJ of electrical energy is dissipated. Determine the voltage across the resistor.
Date posted:
March 26, 2019
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Answers (1)
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An electric bulb rated 40W is operating on 240V mains. Determine the resistance of its filament
(Solved)
An electric bulb rated 40W is operating on 240V mains. Determine the resistance of its filament
Date posted:
March 26, 2019
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Answers (1)
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The figure below shows a wave profile. Determine the frequency of the wave.
(Solved)
The figure below shows a wave profile. Determine the frequency of the wave.
Date posted:
March 26, 2019
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Answers (1)
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One range of frequencies used in broadcasting varies from 0.5 x 100 Hz to 2.0 x 107 Hz. What is the longest wavelength of this...
(Solved)
One range of frequencies used in broadcasting varies from 0.5 x 100 Hz to 2.0 x 107 Hz. What is the longest wavelength of this range? Velocity of light air =3x108/s
Date posted:
March 26, 2019
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Answers (1)
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Explain how you would make a diffraction grating on a piece of glass slide.
(Solved)
Explain how you would make a diffraction grating on a piece of glass slide.
Date posted:
March 26, 2019
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Answers (1)
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Using a pulley system, a girl lifts a load of 1800N using an effort of 400N. If the system is 65% efficient, determine the velocity...
(Solved)
Using a pulley system, a girl lifts a load of 1800N using an effort of 400N. If the system is 65% efficient, determine the velocity ratio of the system.
Date posted:
March 26, 2019
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Answers (1)
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The figure below shows how the potential Energy (P.E) of a ball thrown vertically upwards.
(Solved)
The figure below shows how the potential Energy (P.E) of a ball thrown vertically upwards.
On the same axes, plot a graph of kinetic energy of the ball.
Date posted:
March 26, 2019
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Answers (1)
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The figure below shows a force distance graph for a car being on a horizontal ground
(Solved)
The figure below shows a force distance graph for a car being on a horizontal ground
a) Calculate the total work done
b) If the velocity just before reaching point D is 6m/s, calculate the power developed by the agent providing the force at this point.
c) An electric pump can raise water from a lower-level reservoir to the high level reservoir to the high level reservoir at the rate of 3.0 x 105 kg per hour. The vertical height of the water is raised 360m. If the rate of energy loss in form of heat is 200 kW, determine the efficiency of the pump.
Date posted:
March 26, 2019
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Answers (1)
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Sketch a labeled diagram to show how an arrangement of a single pulley may be used to provide a mechanical advantage of 2.
(Solved)
Sketch a labeled diagram to show how an arrangement of a single pulley may be used to provide a mechanical advantage of 2.
Date posted:
March 26, 2019
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Answers (1)