Where speed is distance/time, velocity is displacement/time.
What this means is that velocity is the length covered in relation to the starting point.
Speed is just the distance travelled no matter where you began.
When going around a circular track, you might have a speed value. However, since you get back to the same location at every lap, you have 0 velocity.
Hope I helped :)
A hypothesis is a proposed explanation made on the basis of limited information while a theory is a series of ideas intended to explain something.
Let h = distance (m) to the water surface.
Initial velocity, u = 0 (because the stone was dropped).
Use the formula
h = ut + (1/2)gt^2
where g = 9.8 m/s^2 (acc. due to graity)
t = time (s)
h = (1/2)*(9.8)*(3^2) = 44.1 m
The Earth is a sphere is a statement to describe a scientific law