Question

• What will be the gain in the mass of
an electron whose kinetic energy is 5 MeV.​

Answer 1

Saini bookstore sold books worth Rs 3,25,645 in the first week of the month and books worth Rs 5,01,496 in the second week of that month. How much was the sale for the two weeks together?

Answer 2

Answer:

The gain in the mass of an electron whose kinetic energy is 5 MeV is 0.8889×$10^{-29}$ kg.

Concept:

According to the energy-mass equivalence we have,

                                     $E = mc^{2}$

For a change in energy, there will be an equivalent change in mass.

We have,

ΔE = Δmc²      --------- (i)

Given:

Kinetic energy, ΔE = 5 MeV = 5×$10^{6}$ eV = 5×$10^6$×1.6×$10^{-19}$ J

                                = 8×$10^{-13}$ J

Solution:

Using equation (i), we get,

ΔE = Δmc²  

8×$10^{-13}$  = Δm (3×$10^8$)²

Δm = $\frac{8X10^{-13}}{(3X10^8)^2}$

Δm = (8×$10^{-13}$) / 9×$10^{16}$

Δm = 0.8889×$10^{-13-16}$ kg

Δm = 0.8889×$10^{-29}$ kg

Gain in mass = Δm = 0.8889×$10^{-29}$ kg

Hence, the gain in the mass of an electron whose kinetic energy is 5 MeV is 0.8889×$10^{-29}$ kg.

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