Index Exceeds number of array elements (1) (Line 19)

Hi, so i am new to Matlab and I am trying to do an assignment that solves for an unknown mass in a elastic collision. Everytime I run the equation that I have derived, I get the error "Index exceeds number of array elements (1)" on the line solving for m1. Any solution would be appreciated, thanks so much.

clear    % clears all variables in the Workspace, avoids common errors

% ----- given information -----

m2 = 150;   % mass of car 2, in g
v1i = 30;   % initial velocity of car 1, in cm/s
v2i = -30;   % initial velocity of car 2, in cm/s
v1f = 0;   % the final velocity wanted for car 1 after collision, in cm/s

% ----- calculations -----

m1 = m2(v1i + v1f - 2 * v2i) / (v1i - v1f)   % mass of first car, derived
                                             % from equation on paper
M = m1+m2   % total mass of both cars, in g

Answer 1

[Walter Roberson]

I would suggest that when you wrote

m2(v1i + v1f - 2 * v2i)

that you were thinking of multiplication between m2 and (v1i + v1f - 2 * v2i) . However, MATLAB has no implicit multiplication anywhere (that I can think of); the expression A(B) in MATLAB means either array A indexed at locations given by B, or else a function named A called with the single parameter B. MATLAB uses .* and * as the multiplication operators, with .* being used for element-by-element multiplication, and * being used for algebraic matrix multiplication.