Answer:
4 m/s
Explanation:
E = mgh and h = E/mg
So if you put your numbers in the formula : h = 4000J/500 * 10
you will get h = 4/5 meters
use this , If the elevator moves from top to the ground in a constasnt acceleration you will have all energy (4000 J) transformed into acceleration to speed up its motion.
(All potential energy will be turned into movement energy). As explained in this formula;
mgh = mv²/2 , solve out (v) from the equation
v = √2gh = √2·10·4/5 (digits are together- not related to the problem, just for clarification) = 4 m/s
Answer the velocity of the elevator is
4 m/s