The normal force acts to counter the gravitational force, that is the upward direction.
The use of pesticides in farming land is example of non-point source pollution. The area of emitting of pollution is very large. That is why, it is difficult to monitor and control this type of pollution.
Americans get their water for everyday use through aquifer. Aquifers can be conserve by avoiding high amount of chemical uses and reducing household waste. Also the sustainable use of water cause conservation of natural resource.
Aquifer are basically underground water present in ground pores. The structure of aquifer just look like sponge. The water moves through the porous surfaces of the ground.
Answer:

Explanation:
The heaviside function is defined as:

so we see that the Heaviside function "switches on" when
, and remains switched on when 
If we want our heaviside function to switch on when
, we need the argument to the heaviside function to be 0 when 
Thus we define a function f:

The
term inside the heaviside function makes sure to displace the function 5 units to the right.
Now we just need to add a scale up factor of 240 V, because thats the voltage applied after the heaviside function switches on. (
when
, so it becomes just a 1, which we can safely ignore.)
Therefore our final result is:

I have made a sketch for you, and added it as attachment.