Lorentz transformations instead of Newtonian
mechanics, Einstein discovered an unexpected
by-product of these calculations to be an E mc 2
energy term which does not vanish at zero
speed. He called it rest mass energy - energy Where E is energy, m is mass, and c is the
which every mass must possess even when speed of light. The speed of light = 299 792
being at rest. The amount of energy is directly 458 m/s = 2.9 x 108 m/s
proportional to the mass of body:
Kinetic Energy (Ek) Potential Energy (Ep)
The energy of a body or a system with respect to Potential Energy is the stored energy in an
the motion of the body or of the particles in the object or system because of its position or
Kinetic energy can be transferred from one Potential energy cannot be transferred.
moving object to another.
Flowing water, such as when falling from a Water at the top of a waterfall, before the
Kinetic energy (KE) or Ek= 1⁄2 mv2 Potential energy (PE) or Ep = mgh
(m= mass, v= velocity) (m=mass, g= gravity, h= height)
LAW OF CONSERVATION OF ENERGY
“Energy cannot be created or destroyed; it Examples :
can only be changed from one form to
another.” - Albert Einstein A television changes electrical energy into
sound and light energy.
It states that the total energy of an isolated
system cannot change. It is said to be A toaster changes electrical energy into
conserved over time. Energy cannot be created thermal energy and light.
or destroyed, but can change form; for
instance, chemical energy can be converted to A car changes chemical energy from fuel into
kinetic energy. thermal energy and mechanical energy.
Energy Transformation Thermal energy is the total kinetic energy of
a substance’s atoms and molecules. Atoms and
Energy can change from one type to molecules are constantly in motion. When
another. This is called an energy thermal energy causes particles to move faster
conversion or energy transformation. and farther apart, the result is a phase change
In energy transformations, some energy is (or change of state).
always lost to the environment as thermal