% Exam 1
% Problem 4

clear all; clc; close all
format long

syms a b l W mu P NA NB

list={a, b, l, W, mu};
listn={5, 24.5, 25, 25, 0.3};

rA=[a, 0, 0];
rB=[0, b, 0];
rC=[a/2, b/2, 0];

G=[0, -W, 0];
FC=[P, 0, 0];
FA=[-mu*NA, NA, 0];
FB=[NB, 0, 0];

% sum F
R = G+FA+FB+FC;
% sum M_A
MA=cross(rB-rA, FB)+cross(rC-rA, FC+G);

sol=solve(R(1),R(2),MA(3),'P, NA, NB');

NAs=sol.NA;
NBs=sol.NB;
Ps=sol.P;
NAn=eval(subs(NAs,list,listn));
NBn=eval(subs(NBs,list,listn));
Pn=eval(subs(Ps,list,listn));

fprintf('NA = %s = %g (lb)\n',char(NAs),NAn);
fprintf('NB = %s = %g (lb)\n',char(NBs),NBn);
fprintf('P = %s = %g (lb)\n',char(Ps),Pn);

NA = W = 25 (lb)
NB = W*(a-b*mu)/b = -2.39796 (lb)
P = -W*(-2*b*mu+a)/b = 9.89796 (lb)

Published with MATLAB® 7.4