If someone where to throw a eraser so it landed 5 meters away and at the exact same time someone just dropped an eraser which would hit the ground first?

It is gravity that pulls the eraser down and since gravitational acceleration is the same for both erasers (as it always is with any 2 objects on earth), the fact the erasers started at the same height means they'll drop to the ground at the same time. note that the horizontal components of velocity doesn't affect the vertical components. to put it in other words, just because one eraser is moving horizontally, it's ability to move vertically is NOT affected compared to an eraser not moving horizontally.

let know if you have any questions!