# Center of gravity

1. Nov 20, 2009

### jaikvk

To find the center of gravity of a 3-D object? The problem is to balance a body in water so that it moves in a straight line when propelled. As the weight distribution in the body is not even it is tilted to one side and when propelled tuns in the direction of tilt. How can the body be made to move in a straight line?

2. Nov 20, 2009

### FoxCommander

Well to find the center of gravity you must do some calculus and find the summation of all the point particls in the object and their gravitys, divided by the mass..... i think. well once you find the postions, any force acting in the direction of the center of gravity will be like acting on all of the point particles at once, therefore making it go in a straight line

3. Nov 20, 2009

### Gerenuk

To find the center of gravity you would calculate
$$\vec{x}_c=\frac{\iiint \vec{x}\mathrm{d}m}{M}$$

However it might not be relevant in the way you imagine. The shape of the object is very important for a stable position. I have an article that describes how the moment of pitch and rolling should behave for the thing to keep a stable position. Let me know if you'd like to read the article and the involved maths.

Moreover, turning one direction doesn't depend on the center of gravity either. Only the shape of the boat determines if it will turn. Of course if the center of gravity is too high, then the boat tilts, changes the shape of the part submersed in water and thus turns.

Basically if you want your boat to float I assume you should have a symmetrical boat and lower the center of gravity. By how much to lower is hard to tell anyway.

4. Nov 24, 2009

### jaikvk

Could you please send me the article

5. Nov 24, 2009

### Gerenuk

sent you a PM

6. Nov 24, 2009

### LeonStanley

Are you sure it is not the gyro effect of the propeller that is tilting the boat and causing it to turn? It may already be perfectly balanced?