AP Physics 2mediummcq1 pt

An electron moves in a circular path of radius 2.0 cm in a uniform magnetic field of 0.50 T. What is the speed of the electron?

A.C) 1.8 × 10^8 m/s

B.A) 1.8 × 10^7 m/s

C.B) 3.6 × 10^7 m/s

D.D) 3.6 × 10^8 m/s

Explanation

Core Concept

When a charged particle moves perpendicular to a magnetic field, the magnetic force provides the centripetal force for circular motion: qvB = mv²/r. Solving for v gives v = qBr/m. For an electron, q = 1.6 × 10^-19 C and m = 9.11 × 10^-31 kg. Therefore, v = (1.6 × 10^-19 C)(0.50 T)(0.020 m)/(9.11 × 10^-31 kg) ≈ 1.8 × 10^7 m/s.

Correct Answer

BA) 1.8 × 10^7 m/s

Practice more AP Physics 2 questions with AI-powered explanations

Practice Unit 5: Magnetism and Electromagnetic Induction Questions →