Answer :
The work needed to stop an object is equal to the kinetic energy of the object:
[tex]K=\frac{1}{2}mv^2[/tex]Write the speed in meters per second using the fact that 1m/s=3.6km/h. Then, the work needed to stop the car is:
[tex]W=\frac{1}{2}(900kg)\left(106\frac{km}{h}\times\frac{1\frac{m}{s}}{3.6\frac{km}{h}}\right)^2=390,138.88...J[/tex]Therefore, the work that must be done to stop the car is approximately 390,139J.