How do I get the matrix p

Hello,

I am trying to solve the a matrix using solve function, not able to figure it out.

clear all
clc
syms x1 x2 M k L dx1 dx2 p
% Displacement of the bar
xg=(x1+x2)/2;
% Rotation of the bar
thi=(x2-x1)/L;
%moment of inertia
J=M*L^2/12;
dxg=(dx1+dx2)/2;
dthi=(dx2-dx1)/L;
% Kinetic energy
KE=0.5*((M*dxg^2)+(J*dthi^2));
% Potenial Engergy
PE=0.5*(2*k*x1^2+3*k*x2^2);
u=[x1 x2];
du=[dx1;dx2];

s=solve(KE==0.5.*transpose(du)*p*du);

[Walter Roberson]

s = solve(EXPRESSION, p)

[LOKESH UDATHA]

Thanks a lot, but a small problem

my p is a 2*2 matrix but I am getting sloution as a scalar.

[Walter Roberson]

No it isn't . u is 1 x 2 so transpose of u is 2 x 1. You cannot do 2 x 1 * 2 x 2 * 1 x 2 because none of the inner dimensions match. Your u would have to be 2 x 1 to fix that .

There is not enough information to isolate 2 x 2 p.

Answer 1

[Sajeer Modavan]

Since you are solving with for p, result of 's' equal to 'p'

to confirm this, you can use following code (which is same as yours, but forcefully solving for 'p')

P = solve(KE==0.5.*transpose(du)*p*du,p);

[LOKESH UDATHA]

Thanks a lot for replying,

but my p is a 2*2 matrix but I am getting p as a scalar.