Calculate the momentum of each of the following objects:
a. A 0.50 kg stone travelling at a velocity of 20 m s⁻¹
b. A 25,000 kg bus travelling at 20 m s⁻¹ on a road
c. An electron travelling at 2.0 × 10⁷ m s⁻¹.
(The mass of the electron is 9.1 × 10⁻³¹ kg.)