An electron travels into a 0.5 T magnetic field perpendicular to its path, where it moves in a circular arc of diameter 0.028 m. What is the kinetic energy of the electron?

6.89 × 10⁻¹³ Joules

Explanation:

Radius of the circular arc = diameter / 2 = 0.028 m / 2 = 0.014 m

radius of the circular arc = mev /qB

me = 9.11 × 10⁻³¹ kg ( mass of an electron)

q of an electron = 1.6 × 10⁻¹⁹ C

B = 0.5 T

v velocity of the electron = r qB / me = (0.014 m ×  1.6 × 10⁻¹⁹ C × 0.5 T) /  (9.11 × 10⁻³¹ kg ) = 0.00123 × 10 ¹² m/s = 1.23 × 10⁹ m/s

Kinetic energy = 1/2 mv² = 0.5 × 9.11 × 10⁻³¹ kg × (1.23 × 10⁹ m/s)² = 6.89 × 10⁻¹³ Joules

c. newton's third law of motion