Is Brain one of the choices?
When an object is slowing down, the acceleration is in the opposite direction as the velocity.
the answer is b.kg/L
the proper answer is 1.0 kg per litre
Mechanical energy = Potential Energy + Kinetic Energy
if there is no friction, M.E. is conserved
as a ball falls, it is losing height. (P.E.=mgh , therefore P.E. will decrease)
the potential energy is transformed into kinetic energy which equals 1/2MV^2.
the increase in K.E. equals the decrease in P.E.
and the sum of both equals M.E.
thus mechanical energy is conserved.
hope this helps you.
