Liquids in physics?

Question

A 8.0-cm-diameter pipe gradually narrows to 2.0 cm. When water flows through this pipe at a certain rate, the gauge pressure in these two sections is 32.0 kPa and 23.0 kPa, respectively. What is the volume rate of flow?

Answer 1

Use Bernoulli's law to calculate energy at both  points in the reducer.

B's Law is a statement of the conservation of energy: in a fluid stream, the energy of the fluid stays the same. In particular, he adds the kinetic energy, potential energy due to elevation, and potention energy due to pressure.

First, assume the reducer is horizontal. This eliminates the elevation (height) term. Remember Q = Area * Velocity.

So, just calculate the energy from pressure and velocity before and after, get two equations in two unkowns (use the Q equation above also), and solve.