How to create matrix array using while loop and time increment?

I have a problem where i want to solve a problem where an apple falls from a tree from 3m before hitting the ground. Assuming there is no air resistance, how long will it take to hit the ground? I have to create an array with time increments until the distance becomes 0 at the final time. So first column should show my time and second column will show the distance going down at every increment.

y0=2;
g=-9.81;

t = 0;
i=0;
y1=y0;

a = zeros([],2);

while y1>=0
    i=i+1;
    t=t+0.10;
    y1=y0-0.5*g*t.^2;
    a(i,:) = [t,y1]
end
disp(a)

    0.0065    2.0726   %sample results
    0.0065    2.0789
    0.0065    2.0853
    0.0065    2.0917
    0.0065    2.0981
    0.0066    2.1046
    0.0066    2.1110
    0.0066    2.1174

But when I run my code, it won't stop running and instead of 0.10 increments, the time looks off. How do I use the while loop (must use) to find the time it takes for the final y value to be 0.

Answer 1

[DGM]

Well, that's what happens when you drop an anti-gravity apple.

y0 = 2;
g = -9.81;
tstep = 0.01;

t = 0;
i = 0;
y1 = y0;
a = zeros([],2);
while y1 >= 0
    i = i + 1;
    t = t + tstep;
    y1 = y0 + 0.5*g*t.^2;
    a(i,:) = [t,y1];
end
plot(a(:,1),a(:,2))

[Kenny Gee]

okay, i see where i made my mistake. sorry about the actual equation. I wanted to learn to do while loop. Thank you :)

Answer 2

[David Hill]

y1=y0+0.5*g*t.^2;%needs to be + (gravity is negative)

[Kenny Gee]

yes you are right. Thank you