E. A racing car has a mass of 710kg. It starts from rest and travels 120m in
3.0s. The car undergoes uniform acceleration during the entire 3.0s.
What is the unbalanced force applied to the car?

6300
N

Explanation:
We will employ the following equation of kinematics
x
=
1
2
a
t
2

which describes an object traveling in one dimension with a constant acceleration and an initial velocity of zero.
We know the displacement and the time elapsed so we may solve for the acceleration:
40.0
m
=
1
2
a
(
3.0
s
)
2

Solving for
a
yields:
a
=
8.89
m
s
2

Now, knowing the acceleration of the car as well as the mass of the car we can apply Newton's second law, which states
F
net
=
m
a

All we need to do is plug in our values for
m
and
a
:
F
net
=
710
kg
⋅
8.89
m
s
2
=
6311.9
N

Considering the fact that our final answer should have only two significant digits, we will round to the nearest hundred:
F
net