I don't understand: What "pressure differential" must be overcome in order to roll down your car windows? I can understand it being more difficult to swing open your car doors, but what's the problem in rolling down your windows?
Regards,
I’m guessing the water presses hard enough agaisnt the window to cause it to bind against its weather stripping.
When your car is on the ground, the air pressure outside your car is equal to the air pressure inside your car. You or the electric motor only has to handle the weight of the window. Nothing else.
In 30 feet of water, the water pressure outside your car is much higher than the air pressure inside your car. The weight of the water presses in against the window, creating friction on the rubber seals. Now you have to overcome not just the small weight of the window, but the high friction force pressing your window against the rubber seals.
It takes a lot more force that you and your window motor are not able to supply.
Air pressure is about 15 psi. On ground, there is no push on your windows.
Only 10 feet under water, the pressure is about 5 psi more than inside your car.
How big is your driver’s window? Maybe 10” by 15”. that is 150 square inches.
150 square inches x 5 pounds/square inch = 750 pounds.
Go slide your plastic cutting board across your kitchen floor.
Now put 750 pounds on the cutting board and try to slide it across the kitchen floor.
This is why you can’t roll down your window when you are sitting in 10-feet of water. The weight of the water pressing on the window, crushing it up against the window frame, is so strong, you don’t have the strength to roll it down, and your electric window motor does not have the strength to roll it down. Assuming it isn’t immediately flooded with water and shorted out.
The best thing to do if you drive into water is to open your door IMMEDIATELY.
So