Refrigerator was what is commonly used today. We do dry foods and salt cure but that is not done on a daily basis
Answer:True
Explanation: The mechanical waves need a medium through which to transport energy because the perturbation travels inside of the medium so it needs molecules that connect elastically the displacement of the wave. For example the sound mainly uses the air molecules to transport the energy also the sound can be traveled in solid materials like metal rods.
It would be option A (a decrease in mass with an increase in volume)
<em>Quantities that determine the kinetic energy of a body are its </em><em>mass and velocity </em>
Answer: <em>mass and velocity </em>
Explanation:
The kinetic energy of a body is the energy possessed by an object by virtue of its motion. It is given by the equation

Where m represents mass of the body and v represents its velocity.
Two bodies of equal velocity but different mass the heavier body will have greater kinetic energy. When an object is at rest its velocity is equal to zero. Thus its kinetic energy will be zero. Hence it can be concluded that only moving bodies have kinetic energy.
Stationary objects placed at a height possess potential energy which is the energy by virtue of their position or configuration. The total mechanical energy of a system is the sum of potential and kinetic energy.