Physics of White Water Rafting Bernoulli Pressure

If you go ever go white water rafting you’ll start out in a nice calm area, kind of like the happy singing place on Splash Mountain in Disneyland.

The river is wide at this point and the velocity of the water is fairly low.

Further down the river though the river will narrow and rocks will be there.

According to Bernoulli, p1 + (1/2)ρv12 = p2 + (1/2)ρv22

Notation:

p is pressure
ρ (rho) is density

and the narrowness will therefore increase the velocity to allow the same amount of water to flow in the same time it takes at the calmer points in the river.

More water has to go through a smaller area so it will need to go faster.

Pressure, equilibrium, and energy conservation

When pressure is exerted it will act and then resolve to equilibrium quickly.

If you squeeze toothpaste it will come out the other end and then stop moving.

Pressure coming from a tire jack can have a very large force, but energy is conserved, so it will be across a small distance.