Answer:
Lifting force, F = 21240 N
Explanation:
It is given that,
Mass of the helicopter, m = 1800 kg
It rises with an upward acceleration of 2 m/s². We need to find the lifting force supplied by its rotating blades. It is given by :
F = mg + ma
Where
mg is its weight
and "ma" is an additional acceleration when it is moving upwards.
So, 
F = 21240 N
So, the lifting force supplied by its rotating blades is 21240 N. Hence, this is the required solution.
Due to difference in electric potential.
<h3>What is Potential difference?</h3>
The amount of work in an electrical field to move a unit charge from one place to another is known as the electrical potential difference.
Here , the potential difference is the difference in electric potential between two charged substances.
Current is the flow of charges from one end end to another end of a conducting wire connected across a two terminals of a battery.
The potential difference is [provided by the battery across the two terminals due which the charges flow.
Current flow is from positive to negative terminals, indicating the movement of positive charges in that direction.
Hence , potential difference causes the electric charges to flow from one end of the battery .
Learn more about the flow of current : brainly.com/question/2264542
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Velocity is distance over time
. If it wants it in km/h you're good to go otherwise if its m/s you need to convert km to m by multiplying 30 by 1000 and t in hours to seconds by multiplying 0.5 by 3600.
Well, almost any website can be, but if you are meaning for money, then google. if you are meaning reliable, then look for something with .org, its history and stuff
Answer:
Decreases by 
times
Explanation:
The intensity of a sound is defined as the energy of the sound that is flowing in an unit time through the unit area which is in the direction that is perpendicular to the direction of the sound waves movement.
The intensity of energy is described by the inverse square law. It states that the intensity varies inversely with the distance square of the distance.
In other words, the sound intensity decreases as inversely proportional to the squared of the distance. i.e. 
In the context when the distance was 3 m, the intensity of the sound was = 
But when the distance became 6 cm or 0.06 m, the sound intensity decreases by = 
= times
