Question #7870d

The formula stated above is Einstein's one of the most famous equation. What this formula represents is that Energy (E) is equal to product of Mass (M) and Speed of light in vacuum squared (c^2).

First, its important to know that we are using speed of light in vacuum. This is a constant and the value of this is:
#299,792,458 m/s#.

Now consider, you need to check how much energy is in One Kilogram. To do this, we know for this purpose

#Mass(M)=1#
Speed of Light#(c)=299,792,458m/s# but for this we will take it as #=2.99792458*10^8#
Energy#(E)=?#

#E=mc^2#

#E=1*(2.99792458*10^8)^2#

#E=8.9875517873681764*10^16J#

Where #J# is energy in Joules

From the above problem, we can guess that #1 kg# of mass have
#8.9875517873681764*10^16J# of energy!

This is the method to to know the energy of certain mass.

Another Concept:

Another method to understand is that energy and mass is convertible into one another. From the above problem, we can understand that we can convert #1kg# of mass into that much energy. But also, we can convert that much energy into #1 kg# of mass. That's why, it is known as the mass-energy equivalence.