First, we have to find the acceleration of the car with the following formula.
![v_f=v_0+at](https://img.qammunity.org/2023/formulas/physics/college/qgre38q8sgm0h17jd2cw9z9w3fnmh5ftbi.png)
Where vf = 0, v0 = 84.21 km/h, and t = 9.260 s. Let's use these values and solve for a.
![\begin{gathered} 0=84.21((km)/(h))+a\cdot9.26\sec \\ -84.21((km)/(h))=a\cdot9.26\sec \\ a=(-84.21((km)/(h)))/(9.26\sec ) \end{gathered}](https://img.qammunity.org/2023/formulas/physics/college/ys8v9nw63e23fx4sm7nh7kr2nif97vh9x5.png)
Before we divide, we have to express the speed in meters per second. We know that 1 km equals 1000 meters, and 1 hour equals 3600 seconds.
![\frac{84.21\operatorname{km}}{h}\cdot\frac{1000m}{1\operatorname{km}}\cdot(1h)/(3600\sec )\approx23.39((m)/(s))]()
Then, we use the transformed speed to find the acceleration.
![a=(-23.39((m)/(s)))/(9.26\sec )\approx-2.53((m)/(s^2))](https://img.qammunity.org/2023/formulas/physics/college/1kihb9yewbmkmmmf7hd80wl1zqsn8w5y4u.png)
Once we have the acceleration, we can find the net force using Newton's Second Law.
![F=ma](https://img.qammunity.org/2023/formulas/physics/high-school/f29csqfwijobd1j24f6y6vv1aba7x8qmg1.png)
Where m = 1,052 kg and a = - 2.53 m/s2.
![F=1052\operatorname{kg}\cdot(-2.53((m)/(s^2)))=-2661.56N]()
Therefore, the net force is 2661.56 Newtons.
The negative sign indicates that the force applied is developing a negative acceleration on the car.