The powder around the hot needle moves away.
Reason
- The high temperature of the needle lowers the surface tension of the water around it.
- High surface tension on the sided pits the powder away
sharon kalunda answered the question on April 3, 2019 at 13:59
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Water in a dam falls through a height 24.5m. If we assume that there are no energy losses,calculate the new temperature of the water as...
(Solved)
Water in a dam falls through a height 24.5m. If we assume that there are no energy losses,calculate the new temperature of the water as it strikes the lower end, given that its initial temperature at the top of the dam is 18.9°C.Take specific heat capacity of water = 4200J/kg
Date posted:
April 3, 2019
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Answers (1)
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The springs A, B, C and D are identical and each extends by 2cm, when a force of 6N is suspended on the system. Determine...
(Solved)
The springs A, B, C and D are identical and each extends by 2cm, when a force of 6N is suspended on the system. Determine the extension of the system
Date posted:
April 3, 2019
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Answers (1)
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The figure below represents a bimetallic strip of metals X and Y at room temperature.
(Solved)
The figure below represents a bimetallic strip of metals X and Y at room temperature.
The figure below shows its shape when dipped into crushed ice
Sketch a diagram in the space given below to show the shape when the strip is heated to a
temperature above the room temperature
Date posted:
April 3, 2019
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Answers (1)
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The figure below shows a bimetallic strip made of brass and iron. A marble is placed at end A of the bimetallic strip as shown below:-
(Solved)
The figure below shows a bimetallic strip made of brass and iron. A marble is placed at end A of the bimetallic strip as shown below:-
State and explain what will be observed when the bimetallic strip is strongly cooled.
Date posted:
April 3, 2019
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Answers (1)
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What do you understand by the statement ‘lower fixed point’ on a temperature scale?
(Solved)
What do you understand by the statement ‘lower fixed point’ on a temperature scale?
Date posted:
April 3, 2019
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Answers (1)
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State two liquids which are used in thermometer
(Solved)
State two liquids which are used in thermometer.
Date posted:
April 3, 2019
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Answers (1)
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Figure shows a beam balance made out of concrete and reinforced with steel.
(Solved)
Figure shows a beam balance made out of concrete and reinforced with steel.
Use a diagram to explain the behaviour of the shape of the beam when heated up.
Date posted:
April 3, 2019
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Answers (1)
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Give a reason why gases are more compressible than liquids
(Solved)
Give a reason why gases are more compressible than liquids
Date posted:
April 3, 2019
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Answers (1)
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An oil drop of average diameter 0.7mm spreads out into a circular patch of diameter 75cm on the surface of water in a trough
(i) Calculate...
(Solved)
An oil drop of average diameter 0.7mm spreads out into a circular patch of diameter 75cm on the surface of water in a trough
(i) Calculate the average thickness of a molecule of oil
(ii) State two assumptions made in (i) above
Date posted:
April 3, 2019
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Answers (1)
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In terms of kinetic theory of matter, explain why evaporation causes cooling
(Solved)
In terms of kinetic theory of matter, explain why evaporation causes cooling
Date posted:
April 3, 2019
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Answers (1)
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The diagram figure below shows a glass tube containing enclosed air by a thread of mercury 50mm
long when the tube is held in a horizontal...
(Solved)
The diagram figure below shows a glass tube containing enclosed air by a thread of mercury 50mm
long when the tube is held in a horizontal position.
(i) The tube is slowly raised in a vertical position with the open end facing up. Determine
the new length of the trapped air (tube has same area of cross-section; atmospheric pressure = 750mmHg)
(ii) Account for the difference in the column of trapped air using kinetic theory of matter assuming that temperature is constant.
Date posted:
April 3, 2019
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Answers (1)
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Explain how an excited hydrogen atom is able to emit radiation of different wavelengths.
(Solved)
Explain how an excited hydrogen atom is able to emit radiation of different wavelengths.
Date posted:
April 3, 2019
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Answers (1)
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A partially filled balloon is placed in a bell jar with its open end on a thick glass plate
as shown in figure. The contact between...
(Solved)
A partially filled balloon is placed in a bell jar with its open end on a thick glass plate
as shown in figure. The contact between the jar and the glass plate is greased to make it air tight:
State and explain what happens to the balloon when air in the ball jar is slowly evacuated.
Date posted:
April 2, 2019
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Answers (1)
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What is the experimental evidence that shows that molecules in gases and liquids are in a state of motion
(Solved)
What is the experimental evidence that shows that molecules in gases and liquids are in a state of motion
Date posted:
April 2, 2019
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Answers (1)
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You are provided with a long glass-tube, fitting corks, cotton wool, concentrated solution hydrochloric acid and concentrated ammonia solution.
(Solved)
You are provided with a long glass-tube, fitting corks, cotton wool, concentrated solution hydrochloric acid and concentrated ammonia solution.
(i) Draw a possible set-up to compare the rates of diffusion of ammonia gas and hydrochloric acid gas
(ii) Outline a clear procedure on how the experiment can be carried out.
(iii) What are the possible observations and conclusion
Date posted:
April 2, 2019
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Answers (1)
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Draw the cross-section of a basic solar heating panel that uses heat from the sun to warm
water which flows through pipes
(Solved)
Draw the cross-section of a basic solar heating panel that uses heat from the sun to warm
water which flows through pipes
Date posted:
April 2, 2019
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Answers (1)
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Distinguish between natural and forced convection currents.
(Solved)
Distinguish between natural and forced convection currents.
Date posted:
April 2, 2019
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Answers (1)
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The total weight of a car with passengers is 25,000N. The area of contact of each of the four
tyres with the ground is 0.025m2. Determine...
(Solved)
The total weight of a car with passengers is 25,000N. The area of contact of each of the four
tyres with the ground is 0.025m2. Determine the minimum car tyre pressure
Date posted:
April 2, 2019
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Answers (1)
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A block measuring 20cm x 10cm by 5cm rests on a flat surface. The block has a weight of 3N.
Determine the maximum pressure it exerts...
(Solved)
A block measuring 20cm x 10cm by 5cm rests on a flat surface. The block has a weight of 3N.
Determine the maximum pressure it exerts on the surface.
Date posted:
April 2, 2019
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Answers (1)
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The figure shows a liquid in a pail.
(Solved)
The figure shows a liquid in a pail.
Suggest a reason why pail manufacturers prefer the shape shown to other shapes
Date posted:
April 2, 2019
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Answers (1)