Chapter 4 - Force and Motion - Learning Path Questions and Exercises - Conceptual Questions - Page 134: 20

Such a vertical downward force is desired in order to reduce the normal force (N) which will in turn reduce the kinetic friction and the Indy racing car can move faster. By making the car heavier just makes the normal force higher. This will cause the kinetic friction force higher and restricts the movement of the car which is not desirable.

Such a vertical downward force is desired in order to reduce the normal force (N) which will in turn reduce the kinetic friction and the Indy racing car can move faster. By making the car heavier just makes the normal force higher. This will cause the kinetic friction force higher and restricts the movement of the car which is not desirable.