Final answer:
Applying the physical principle that skid distance is proportional to the square of the speed, the car that skids 17 m at 42 km/h would skid 153 m at 126 km/h, assuming constant conditions.
Step-by-step explanation:
The subject of this question is physics, primarily focusing on the principles of motion, force, and friction. The question involves calculating the distance a car would skid with locked brakes at different speeds, applying the laws of physics regarding friction and acceleration. When a car moving at 42 km/h skids 17 meters with locked brakes, to find out how far it will skid at 126 km/h (three times the initial speed), we can use the concept that the skid distance is proportional to the square of the speed. By setting up the appropriate proportion (assuming the friction coefficient and other conditions remain constant), the calculation would show that at 126 km/h, the skid distance would be nine times as much, because skid distance varies with the square of the speed. Therefore, if a car skids 17 m at 42 km/h, at 126 km/h it would skid 17 m * 9 = 153 m.