# Revision history [back]

### solving a physic problem using sage

Hi, I'm new in this community.

I want to solve a physic problem which requires differential equation system solutions.

I don't know if my equations are correctly set. Any suggestion is good. My problem is described by this image: http://img805.imageshack.us/img805/7043/lllzm.png

I have two masses (1/3m the first, 2/3m the second) linked with a rope. The rope is free to slide around a nail (the big black point in the image). The image shows the starting condition: a man keeps the first mass stopped and so the rope is kept stretched by the second mass.

I search three functions describing the kinematics of two masses after the man will leave the fist mass: vertical movement of mass A y(t), vertical movement of mass B j(t), and horizontal movement of mass B x(t).

My Cartesian reference system is x-y system in the image.

I have to solve the following equations: 1) -2/3mg+T=2/3md2/dt2_y 2) -1/3mg+Sy=1/3md2/dt2_j 3) Sx=1/3m*d2/dt2_x 4) abs(T)=sqrt(Sx^2+Sy^2) 5) abs(y(t))=sqrt(x(t)^2+j(t)^2)

From the forth and the fifth equations I obtain two equations, so I have 5 equations in 5 unknowns. They are: 1) T force sustaining the second mass 2) Sx x-component of force sustaining the first mass 3) Sy y-component of force sustaining the first mass 4) y(t) position of the second mass 5) x(t) x-position of the first mass 6) j(t) y-position of the first mass

I hope my explanation is clear.

How can I obtain my solutions using Sage?

Thank you very much!!

### solving a physic problem using sage

Hi, I'm new in this community.

I want to solve a physic problem which requires differential equation system solutions.

I don't know if my equations are correctly set. Any suggestion is good. My problem is described by this image: http://img805.imageshack.us/img805/7043/lllzm.png

I have two masses (1/3m the first, 2/3m the second) linked with a rope. The rope is free to slide around a nail (the big black point in the image). The image shows the starting condition: a man keeps the first mass stopped and so the rope is kept stretched by the second mass.

I search three functions describing the kinematics of two masses after the man will leave the fist mass: vertical movement of mass A y(t), vertical movement of mass B j(t), and horizontal movement of mass B x(t).

My Cartesian reference system is x-y system in the image.

I have to solve the following equations: 1) -2/3mg+T=2/3md2/dt2_y 2) -1/3mg+Sy=1/3md2/dt2_j 3) Sx=1/3m*d2/dt2_x 4) abs(T)=sqrt(Sx^2+Sy^2) 5) abs(y(t))=sqrt(x(t)^2+j(t)^2)

From the forth and the fifth equations I obtain two equations, so I have 5 equations in 5 unknowns. They are: 1) T force sustaining the second mass 2) Sx x-component of force sustaining the first mass 3) Sy y-component of force sustaining the first mass 4) y(t) position of the second mass 5) x(t) x-position of the first mass 6) j(t) y-position of the first mass

I hope my explanation is clear.

How can I obtain my solutions using Sage?

Thank you very much!!

### solving a physic problem using sage

Hi, I'm new in this community.

I want to solve a physic problem which requires differential equation system solutions.

I don't know if my equations are correctly set. Any suggestion is good. My problem is described by this image: http://img805.imageshack.us/img805/7043/lllzm.png

I have two masses (1/3m the first, 2/3m the second) linked with a rope. The rope is free to slide around a nail (the big black point in the image). The image shows the starting condition: a man keeps the first mass stopped and so the rope is kept stretched by the second mass.

I search three functions describing the kinematics of two masses after the man will leave the fist mass: vertical movement of mass A y(t), vertical movement of mass B j(t), and horizontal movement of mass B x(t).

My Cartesian reference system is x-y system in the image.

I have to solve the following equations: 1) -2/3mg+T=2/3md2/dt2_y 2) -1/3mg+Sy=1/3md2/dt2_j 3) Sx=1/3m*d2/dt2_x 4) abs(T)=sqrt(Sx^2+Sy^2) 5) abs(y(t))=sqrt(x(t)^2+j(t)^2)

From the forth and the fifth equations I obtain two equations, so I have 5 equations in 5 unknowns. They are: 1) T force sustaining the second mass 2) Sx x-component of force sustaining the first mass 3) Sy y-component of force sustaining the first mass 4) y(t) position of the second mass 5) x(t) x-position of the first mass 6) j(t) y-position of the first mass

I hope my explanation is clear.

How can I obtain my solutions using Sage?

Thank you very much!! 4 fix formating

### solving a physic problem using sage

Hi, I'm new in this community.

I want to solve a physic problem which requires differential equation system solutions.

I don't know if my equations are correctly set. Any suggestion is good. My problem is described by this image: http://img805.imageshack.us/img805/7043/lllzm.png

I have two masses (1/3m the first, 2/3m the second) linked with a rope. The rope is free to slide around a nail (the big black point in the image). The image shows the starting condition: a man keeps the first mass stopped and so the rope is kept stretched by the second mass.

I search three functions describing the kinematics of two masses after the man will leave the fist mass: vertical movement of mass A y(t), vertical movement of mass B j(t), and horizontal movement of mass B x(t).

My Cartesian reference system is x-y system in the image.

I have to solve the following equations: 1) -2/3mg+T=2/3md2/dt2_y 2) -1/3mg+Sy=1/3md2/dt2_j 3) Sx=1/3m*d2/dt2_x 4) abs(T)=sqrt(Sx^2+Sy^2) 5) abs(y(t))=sqrt(x(t)^2+j(t)^2)

1. $-\frac{2}{3}mg+T=\frac{2}{3}m \frac{d^2y}{dt^2}$
2. $-\frac{1}{3}mg+S_y=\frac{1}{3}m\frac{d^2j}{dt^2}$
3. $S_x=\frac{1}{3}m\frac{d^2x}{dt^2}$
4. $|T|=\sqrt{S_x^2+S_y^2}$
5. $|y(t)|=\sqrt{x(t)^2+j(t)^2}$

From the forth and the fifth equations I obtain two equations, so I have 5 equations in 5 unknowns. They are:

1) T force sustaining the second mass

2) Sx x-component of force sustaining the first mass

3) Sy y-component of force sustaining the first mass

4) y(t) position of the second mass

5) x(t) x-position of the first mass

6) j(t) y-position of the first mass

I hope my explanation is clear.

How can I obtain my solutions using Sage?

Thank you very much!! 5 retagged FrédéricC 2539 ●3 ●28 ●53

### solving a physic problem using sage

Hi, I'm new in this community.

I want to solve a physic problem which requires differential equation system solutions.

I don't know if my equations are correctly set. Any suggestion is good. My problem is described by this image: http://img805.imageshack.us/img805/7043/lllzm.png

I have two masses (1/3m the first, 2/3m the second) linked with a rope. The rope is free to slide around a nail (the big black point in the image). The image shows the starting condition: a man keeps the first mass stopped and so the rope is kept stretched by the second mass.

I search three functions describing the kinematics of two masses after the man will leave the fist mass: vertical movement of mass A y(t), vertical movement of mass B j(t), and horizontal movement of mass B x(t).

My Cartesian reference system is x-y system in the image.

I have to solve the following equations:

1. $-\frac{2}{3}mg+T=\frac{2}{3}m \frac{d^2y}{dt^2}$
2. $-\frac{1}{3}mg+S_y=\frac{1}{3}m\frac{d^2j}{dt^2}$
3. $S_x=\frac{1}{3}m\frac{d^2x}{dt^2}$
4. $|T|=\sqrt{S_x^2+S_y^2}$
5. $|y(t)|=\sqrt{x(t)^2+j(t)^2}$

From the forth and the fifth equations I obtain two equations, so I have 5 equations in 5 unknowns. They are:

1) T force sustaining the second mass

2) Sx x-component of force sustaining the first mass

3) Sy y-component of force sustaining the first mass

4) y(t) position of the second mass

5) x(t) x-position of the first mass

6) j(t) y-position of the first mass

I hope my explanation is clear.

How can I obtain my solutions using Sage?

Thank you very much!!