Question

what is the height of object of mass 4kg which touches the ground after 5 seconds?​

Answer 1

If it is dropped from 16 feet, in one second it has hit the ground, and then (or soon after) its kinetic energy is zero

Explanation:

If you are close to the Earth but not that close, the speed after 5 s. is v=gt or v=9.8m/s/s * 5 s = 49 m/s. Since KE= (1/2)m(v**2) you get (1/2)(49**2)(4kg) in joules. Multiply it.