# Fluid resistance (drag)

1. Jan 22, 2006

### itsjustme

Is there any relationship (formula) that can determine the force of drag to an object. thx in advance.

2. Jan 22, 2006

### mtong

Drag is directly proportional to velocity squared. Hence Drag=C * V^2 where c is a constant and v is the velocity of the body relative to the fluid. The usual form is Drag=1/2 CpAv^2. Where C is the drag coefficient, p is the Greek letter rho representing the density of the fluid and A the effective cross sectional area.

Note: Before just asking for a formula try google or wikipedia in future.

3. Jan 22, 2006

### itsjustme

ok thanks hmm c, i have my doubts about it being the speed of light what constant is it?

4. Jan 22, 2006

### mtong

c would be the constant of proportionality. eg. if y directly varies with x then the relationship between y and x will be y=kx; Where k is a constant whose value is determined to fit a set of data.

http://www.purplemath.com/modules/variatn.htm

In the case above the constant will take the form 1/2 CpA wich will be determined by the fluid and object.

5. Jan 22, 2006

### Pyrrhus

Last edited by a moderator: Apr 21, 2017