A person is sitting in a car which is at rest. The reaction from the road at each of the four wheels of the car is R. When the car runs on a straight level road, how will the reaction at either of the front wheels vary?

When the car accelerates, a horizontal force is applied to change its state of motion; forces are responsible for changing speed or direction of objects [1]. In a vehicle, the forward driving force comes from tyre–road static friction which accelerates the car relative to the road. During acceleration, the inertial (pseudo) effect shifts the load toward the rear wheels, reducing the normal (reaction) on the front wheels. Thus the reaction at either front wheel becomes less than R (it was R when the car was at rest). This is a consequence of longitudinal acceleration causing load transfer rearwards, so front-wheel normal force decreases below the static value R.

Sources

1. [1] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 5: Exploring Forces > Activity 5.2: Let us analyse > p. 65