Now the net force on the window (and other parts of the truck) will be near zero. The trick is to increase the pressure within the truck such that the interior pressure is the same as the exterior pressure. You can't build a constant internal pressure submarine with these types of materials.īut you can still make a submatruck (I like that word) that can dive to 30 meters without breaking a window. What if the submatruck descended to 300 meters? Yes, the glass would clearly break. Do you think it would support them? I don't.
Just imagine 2 very large men standing on that glass. But trust me, this calculation will work.Ī force of 1960 Newtons is rather large for a truck window. Yes, I made the approximation that the pressure on the window is constant but in fact it increases with depth. Assuming the window is 20 cm by 20 cm and at a depth of 5 meters, the total force is 1960 Newtons (440 pounds). In this expression, ρ is the density of the water and g is the gravitational constant. Fresh water has a density of around 1000 kg/m 3 and the pressure dependence on depth would be: So, in the end this is equivalent to only the force due to the pressure from the water. Inside the truck, the force is due to the 1 atmosphere of air. Outside the window, the force is exerted by the atmosphere and 5 meters of water.
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