WhenEvent "StopIntegration" problem

Question

The first example on the WhenEvent help page is

NDSolve[{y''[t] == -9.81, y[0] == 5, y'[0] == 0, 
   WhenEvent[y[t] == 0, y'[t] -> -0.95 y'[t]]}, y, {t, 0, 10}];

Say I want to stop the integration at the first bounce, I would put

NDSolve[{y''[t] == -9.81, y[0] == 5, y'[0] == 0, 
   WhenEvent[y[t] == 0,"StopIntegration"]}, y, {t, 0, 10}];

That, however, does not stop the integration (i.e. it goes on to t=10), neither does the condition y[t] < 0. What am I doing wrong?

Answer 1

Try this:

ySol = NDSolveValue[{y''[t] == -9.81, y[0] == 5, y'[0] == 0, 
   WhenEvent[y[t] == 0, {tMax = t, "StopIntegration"}]}, 
  y, {t, 0, 10}];
Plot[ySol[x], {x, 0, tMax}]

And in tMax you'll get 1.00964, that's slightly larger than t when y[t] = 0.