Lets say you are traveling at a speed of 80, and there are no other variables like braking and acceleration, and you hit a giant puddle with the wheels COMPLETELY straight, why would the car suddenly jerk in one direction causing a spinout? Shouldn’t the car just continue in the direction of the wheels regardless of traction loss?
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Newton’s First Law of Motion – an object in motion will remain in motion unless a force acts on it. Newton was talking about straight line movement, but rotational motion (angular momentum) is also conserved in the absence of other forces.
Let do a thought experiment, and replace water on the road with a big flat frozen lake, strong enough to support the car. Drive straight a road on to the ice. The car will keep going forward in a straight line (no other forces acting on it) until it slows down due to friction and air resistance.
Now lets say you jerk the steering a bit as you transition on to the ice. Your car now has a bit of angular momentum. There isn’t enough friction from the tyres to stop the car from continuing to rotate (because angular momentum is also conserved). So now you slide across the ice slowly rotating.
The same things should happen if you hit water and hydroplane on a road. But the layer of water lifting your tyre off the road is very thin, and not always stable. Maintaining four tyres equally off the road surface is almost impossible for any length of time, so it is very likely that one tyre will drag or push, so rotation starts. Then a tyre might be going sideways when the lifting layer of water collapses, and the sidewall of that tyre catches the surface of the road, and the car is out of control.
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