Kinetic energy is an
expression of the fact that a moving object can do work on anything it hits; it
quantifies the amount of work the object could do as a result of its motion. It
can be calculated as:
KE
= mv^2 /2
We
calculate the problem as follows:
KE
= mv^2 /2
400
= m(20)^2 / 2
m
= 2 kg
