7) c
opposite charges attract, equal charges repell
8) c
Followed from equation
9) d
Same reason as under 7
Explanation:
We often refer to the electricity at a typical household outlet as being 120 V. In fact, the voltage of this AC source varies; the 120 V is "the rms value of the voltage".
The rms value of voltage is given by :

Where
is the peak value of voltage
So, the correct option is (d). " rms value of voltage".
The Joule is the SI unit of energy.
Answer:
high pressure system in the air moves up and brings good weather
give me thanks >:(
Answer: 5 m
Explanation:
We have the following data:
is the intensity of the sound at 7.5 m from the source
is the distance at which the intensity
was measured
is the intensity of the sound at
from the source
We have to find 
Since the object is radiating the signal uniformly in all directions, we can use the <u>Inverse Square Law for Intensity:</u>

Isolating
:


This is the distance at which the intensity is the "threshold of pain"
Now, we have to substract this value to
to find how much closer to the source can we move:
