Answer:
The hammer's velocity when it strikes the ground is 128 ft/s. 
Explanation:
Given that,
The distance (in feet) the hammer falls in t sec is given by the relation as :

The hammer is accidentally dropped from a height of 784 ft. We need to find the hammer's velocity when it strikes the ground. We know that the velocity of an object is equal to :

When the hammer strikes ground, s = 256 ft
So,

So, the velocity of the hammer when it strikes the ground is given by :

So, the hammer's velocity when it strikes the ground is 128 ft/s. Hence, this is the required solution.