A scientist performs an experiment involving the collision of two masses on a flat surface. She believes she has made a startling discovery: the total kinetic energy is not conserved. What might she have overlooked?
A.
Some gravitational potential energy may have been gained.
B.
Some gravitational potential energy may have been lost.
C.
Some energy may have been gained due to friction and/or sound.
D.
Some energy may have been lost due to friction and/or sound.