function F = start1(W,M)
% S.Moor March 2005
% Calculates the static friction for one of four specific cases
% given the case and the weight. Input from command line
%
% F=start1(W,M)
% The four Cases
% 1. Metal on metal
% 2. Wood on wood
% 3. Metal on wood
% 4. Rubber on concrete
%
% variables
% Inputs    W = weight of the object (lbm)
%           M = a number representing the material selections as shown above
% Output:   F = force required to over come static friction (lbf)

% Intermedeate variables
% mu = the coefficient of static friction 
 
% switch structure selects the correct coefficient of static friction based
% on material input.  
switch M 
    case 1
        mu = 0.2;
    case 2
        mu =0.35;
    case 3
        mu=0.40;
    case 4
        mu =0.7;
    otherwise
        disp('ERROR: invalid materials choice')
        mu=NaN;
end
% Calculates force required to get object moving
F=mu*W;