Question

how long does stone take to fall 4.9m and what is its speed at the end of that fall

Answer 1

If a stone is falling freely in gravitational field of earth then it will expiernce acceleration of g = 9.8 m/s2.
Now from equation of motion
h = ut -1/2g*t2
here u = 0
so h = 1/2g*t2
t^2 = 2h/g = 2*4.9/9.8
t = 1 s