What is the kinetic energy K of an electron with momentum 1.05×10−24 kilogram meters per second?Express your answer in electron volts to two significant figures.

3.7eV

The kinetic energy (K) of a particle is the half the product of the mass (m) and the square of the velocity (v) of the particle. i.e

K = x m x v²        --------------------(i)

Also, the momentum (p) of a particle is the product of the mass and the velocity of the particle. i.e

p = m x v                   [square both sides]

p² = (mv)²

p² = m²v²                   [make v² subject of the formula]

v² =      

Now substitute v² =  into equation (i) as follows;

K = x m x

K = x          --------------------------(ii)

From the question the particle is an electron with the following details;

m = mass of the electron = 9.1 x 10⁻³¹kg                        [known value]

p = momentum of the electron = 1.05 x 10⁻²⁴kgm/s    [given value]

Substitute these values into equation (ii) as follows;

K = x

K = x

K = x 0.12 x 10⁻¹⁷

K = 0.06 x 10⁻¹⁷

K = 6.00 x 10⁻¹⁹ J

Convert the result to electron volts (eV) as follows;

1 J = 6.2 x 10¹⁸ eV

6.00 x 10⁻¹⁹ J = 6.00 x 10⁻¹⁹ J x 6.2 x 10¹⁸ eV / 1 J = 3.7eV

Therefore, the kinetic energy K of an electron with that momentum is 3.7eV

the moon affects the earth gravitation ally, causing certain motions of that body and also producing tides in its ocean and atmosphere. the tidal wave in our atmosphere is, however, far too minute to be an effective cause in any known meteorological phenomenon.

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