The height of an object dropped from a certain height is modeled by the function $h(t)=-16t^2+b$, where $h(t)$ is the height in feet and $t$ is the time in seconds. Object P is dropped from a height of 2,000 feet. Object Q is dropped from a height of 1,000 feet. Approximately how many more seconds does it take for Object P to hit the ground than for Object Q to hit the ground?