What physics concept underlies these three observations? When passing an oncoming truck on the highway, your car tends to sway toward the truck. The canvas roof of a convertible automobile bulges upward when the car is traveling at high speeds. The windows of older trains sometimes break when a high-speed train passes by on the next track.

The underlying principle is the bernoulli's principle of fluid flow which states that a slow moving air stream exerts more pressure than a faster moving air stream

Explanation:

The air stream between the car and the truck experiences more drag and therefore has a relatively higher speed than the air stream on the other side of the car, this means the air on the other side exerts more side force on the car, the net side force causes the car to swoop sideways towards the truck.

The same applies to a moving convertible car at high speed. The air outside has a higher relative velocity than the air inside the car. The inside air exerts more force on the canvass roof causing it to bulge upwards.

The windows of old train crack due to the pressure from the air within the old train which moves at a lower relative speed to that between the train and the speed train.