Answer:
Sputnik I.
Explanation:
The Soviet Union (former) launched the first artificial earth satellite called Sputnik I on October 4, 1957.
It had a diameter of 58 cm and it weighed 83.6 kg. It had an orbital period of 5880 seconds around the earth. It orbited the 11 weeks (officially 3 weeks but then, its battery died and it orbited for 8 weeks before falling back into the earth's atmosphere).
Answer:
Airplane cabins are pressurized because as the airplane climbs higher in altitude, the air becomes very thin, this pressurization ensures that there is still enough breathable oxygen in the cabin to prevent everyone from suffering the effects of hypoxia and passing out.
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Answer:

Explanation:
A charge located at a point will experience a zero electrostatic force if the resultant electric field on it due to any other charge(s) is zero.
is located at the origin. The net force on it will only be zero if the resultant electric field intensity due to
and
at the origin is equal to zero. Therefore we can perform this solution without necessarily needing the value of
.
Let the electric field intensity due to
be +
and that due to
be -
since the charge is negative. Hence at the origin;

From equation (1) above, we obtain the following;

From Coulomb's law the following relationship holds;

where
is the distance of
from the origin,
is the distance of
from the origin and k is the electrostatic constant.
It therefore means that from equation (2) we can write the following;

k can cancel out from both side of equation (3), so that we finally obtain the following;

Given;

Substituting these values into equation (4); we obtain the following;

