A Level Physics Practice Exam

How many times smaller is the mass of an electron compared to a proton?

1. 500

2. 1000

3. 2000

4. 3000

The correct answer is: 2000

To determine how many times smaller the mass of an electron is compared to a proton, it's essential to look at their relative masses. The mass of an electron is approximately \(9.11 \times 10^{-31}\) kilograms, while the mass of a proton is about \(1.67 \times 10^{-27}\) kilograms. When you divide the mass of a proton by the mass of an electron, you find: \[ \text{Factor} = \frac{\text{mass of proton}}{\text{mass of electron}} \approx \frac{1.67 \times 10^{-27}}{9.11 \times 10^{-31}} \approx 1836 \] This demonstrates that a proton is roughly 1836 times more massive than an electron. However, in contexts where approximations are acceptable, especially in educational settings, this value might be rounded to the nearest significant figure, leading to the choice of approximately 2000. Thus, saying the mass of an electron is 2000 times smaller than that of a proton conveys a simplified yet accurate understanding for initial learning purposes. This reflects a common approach in physics, where exact precision can sometimes be relaxed for clarity.