By a string, a body of mass m is hanging from the ceiling in the center of the passenger car. Body and the string are perpendicular. Next, the passenger car begins to accelerate to the right. Body and the string tilt to the left. This acceleration is usually constant. However, if an external force F continues to grow as time passes, the inclination of body and the string also continues to grow. This varying is the same for one inside and outside the passenger car. And, the tension of the string, which is a reaction to the inertial force will be the same to the two also (and if the string breaks, it will be the same to the two also).
