Answer:
The distance is
=
7
m
Explanation:
Apply the equation of motion
s
(
t
)
=
u
t
+
1
2
a
t
2
The initial velocity is
u
=
0
m
s
−
1
The acceleration is
a
=
2
m
s
−
2
Therefore, when
t
=
3
s
, we get
s
(
3
)
=
0
+
1
2
⋅
2
⋅
3
2
=
9
m
and when
t
=
4
s
s
(
4
)
=
0
+
1
2
⋅
2
⋅
4
2
=
16
m
Therefore,
The distance travelled in the fourth second is
d
=
s
(
4
)
−
s
(
3
)
=
16
−
9
=
7
m
99% of the earth´s atmosphere by mass is made up of only these elements: Nitrogen and oxygen.
Answer: B) Nitrogen and oxygen.
1) C. velocity
Acceleration is defined as the rate of change of velocity per unit time. In formulas:

where
is the change in velocity
is the time interval
Therefore, the correct answer is C. velocity.
2) A. 9.8m/s/s
Earth's gravity is a force, so it produces an acceleration on every object with mass located on the Earth's surface. This acceleration can be calculated, as it is given by the formula

where
is the gravitational constant
is the Earth's mass
is the Earth's radius
By substituting these numbers into the formula, one can find that the acceleration due to Earth's gravity is
.