Answer:
12.5 m/s
Explanation:
The motion of the hammer is a free fall motion, so a uniformly accelerated motion, therefore we can use the following suvat equation:

Where, taking downward as positive direction, we have:
s = 8 m is the displacement of the hammer
u = 0 is the initial velocity (it is dropped from rest)
v is the final velocity
is the acceleration of gravity
Solving the equation for v, we find the final velocity:

So, the final speed is 12.5 m/s.
Answer:
Work, in physics, measure of energy transfer that occurs when an object is moved over a distance by an external force
Explanation:
at least part of which is applied in the direction of the displacement. ... To express this concept mathematically, the work W is equal to the force f times the distance d, or W = fd.
It runs on Hydrogen gas.
Actually, using hydrogen as a fuel is not new. We used to use it on air vehicle like air balloon. But back then, we still cannot figure out how to safely use this because Hydrogen exlodes rather easily