Two friends are comparing a football and a hockey ball on the school playground. The football has a mass of 0.40kg and is lying at rest, while the hockey ball has a mass of 0.15kg and is rolling slowly with a speed of 1.0ms−1. Answer the following questions.
(i) Define (a) inertia and (b) momentum, mentioning their SI units.
(ii) Which of the two balls possesses greater inertia? Give a reason without using numerical calculation.
(iii) Calculate the momentum of the hockey ball. On this basis, state which ball has the greater momentum.
(iv) Explain briefly how your answers to parts (ii) and (iii) illustrate that inertia depends only on mass whereas momentum depends on both mass and velocity.