Solving Diff Eq for Free-fall w/o Drag in Tank Outlet

In summary, the conversation discusses the velocity of liquid flowing out of a tank with an outlet near the bottom. It is shown that the velocity is equal to that of a particle free falling without drag. The conversation then moves on to solving for the rate of outflow and the rate of change of liquid in the tank, using the area of the cross section, contraction coefficient, outlet and gravity. Finally, a specific scenario is given involving a water tank in the shape of a right circular cylinder, with a 3m water level and specific values for radius and constant "b". The question posed is how long it would take to drain the tank to the level of the outlet. The speaker also mentions needing help with part a and asking for someone
  • #1
he lives
1
0
Suppose a tank containing a liquid has an outlet near the bottom. The velocity of the liquid flowing out of the outlet is equal to a particle free falling without drag.

a. show that v=sqrt(2gh)

b. by finding the rate of outflow to the rate of change of the liquid in the
tank, find h(t) that satisfies the equation:
A(h)(dh/dt) = (-b)(a)(sqrt(2gh))

A(h) = the area of the cross section of the tank at height h
b = a contraction coefficient that describes how the water flows (constant)
a = the radius of the outlet
g = gravity (9.81 m/s^2)

c. Consider a water tank in the form of a right circular cylinder. The water level is 3m above the outlet. Radius of tank is 1m radius of outlet is 0.1m. the value for the constant "b" is 0.6 How long does it take to drain the tank to the level of the outlet.

I have solved part a and really need help for the rest. If anyone can help it would be greatly appreciated. Also if you don't mind doing part A i would like to check my method.
 
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  • #2
Hi and welcome to Physicsforums he lives.
Before we help, we need to see some effort on your side. Can you post your attempt at this problem, along with your thoughts or ideas on how to solve it?
 

Related to Solving Diff Eq for Free-fall w/o Drag in Tank Outlet

1. What is a differential equation?

A differential equation is a mathematical equation that relates an unknown function to its derivatives. It describes the relationship between a function and its rate of change.

2. How do you solve a differential equation?

There are several methods for solving a differential equation, including analytical methods such as separation of variables, substitution, and using integrating factors. Numerical methods such as Euler's method and Runge-Kutta methods can also be used to approximate solutions.

3. What is free-fall without drag?

Free-fall without drag is a type of motion where an object is falling due to the force of gravity, but there is no resistance or drag force acting on the object. This type of motion is commonly seen in objects falling in a vacuum or in very dense fluids.

4. What is the tank outlet problem?

The tank outlet problem is a classic example in physics and engineering where a tank is being emptied through an opening at the bottom, and the rate of change of the fluid level in the tank is described by a differential equation.

5. How do you solve a differential equation for free-fall without drag in a tank outlet?

To solve this problem, we can use the general form of the differential equation for free-fall without drag in a tank outlet, which is dV/dt = -k√(V), where V is the volume of fluid in the tank and k is a constant. This equation can be solved using separation of variables and integration to find an expression for V as a function of time.

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