# Degrees of freedom

1. Feb 8, 2013

### Jhansi1990@gma

What are the number of degrees of freedom of
1)a square sheet moving in XY plane
2)a triangular lamina moving freely in XY plane

2. Feb 8, 2013

### Staff: Mentor

This looks like homework: What did you find out so far?

3. Feb 10, 2013

### Jhansi1990@gma

A square is composed of many particles with the constraint that distance between every particle is the fixed.so such a square is moving in XY plane.

if i consider two particles they have 4-1 =3degree of freedom(one is subtracted due to constraint that distance between particles are fixed).if i consider third particle it is defined by two co-ordinates and two constraints and therefore no degree of freedom.....the same for fourth fifth and so on.....

and i dont find any difference in this respect with a triangular lamina......

I do not know the answer to the question.......please comment on this and say if you have any other opinion.

4. Feb 10, 2013

### Staff: Mentor

Those 3 degrees of freedom just fix the current position of the square. What about its movement?

5. Feb 10, 2013

### Jhansi1990@gma

if i get generalized co-ordinates i can calculate co-ordinate velocities from it

6. Feb 10, 2013

### Staff: Mentor

Is that related to the original question?
What do you mean with "get"?

7. Feb 10, 2013

### Jhansi1990@gma

The question does not ask that .But i told a general principle.For example a simple pendulum which is oscillating in a plane.since its moving along the arc of a circle(distance from orgin is fixed) it has only one degree of freedom....theta.....which is the angle dat the string makes with vertical.......so if i know theta as a function of time.....i can differentiate "theta" to find generalised co-ordinate velocity