Question

An electron is traveling at 1% the speed of light. What is its kinetic energy in joules? (Speed of light = 3 x 10 m/s)​

Answer 1

Answer:

1.365×10^-27 joules

Explanation:

1% of speed of light is 300000×1/100 =3000m/s

speed of e (v) = 3000m/s

mass of e (m) = 9.1×10^-31 kg

then,

kinetic energy of e = 1/2mv^2

= 1/2×9.1×10^-31×3000

=1.365×10^-27 joules

Answer 2

Given: An electron is traveling at 1% the speed of light.

To find: Its kinetic energy in joules.

Solution:

• Since the question says that the electron is traveling at 1% the speed of light and the speed of light is 3×10⁸ ms⁻¹, it is calculated as,

        $\frac{1}{100} * 3 * 10^{8} = 3*10^{6} ms^{-1}$

• Kinetic energy of a body is the energy possessed by the virtue of its motion.
• It is calculated using the following formula,

        $K = \frac{1}{2} mv^{2}$

• Here, K is the kinetic energy, m is the mass and v is the velocity of the electron.
• The mass of an electron is 9×10⁻³¹ kg.
• On replacing the terms with the values given in the question,

        $K = \frac{1}{2} (9 * 10^{-31} ) (3 * 10^{6} )^{2}$

            $= 40.5 * 10^{-19} J$

Therefore, the kinetic energy of the electron in joules is 40.5×10⁻¹⁹ J.