For the bullets:

Correct answer: a i and ii

From Q, a = u²/(2s) = 200²/(2 × 0.05) = 4 × 10⁵ ms⁻². Same mass and same tree, so P has the same deceleration and meets the same resistance (ii). Then x² = 2 × 4 × 10⁵ × 0.0405 = 32400, so x = 180 ms⁻¹ (i). Statement iii fails; the answer is i and ii.

Why the other options are wrong

• b i and iii: iii fails: the stopping time is t = u/a, and P and Q start at 180 and 200 with the same deceleration. P stops after 4.5 × 10⁻⁴ s and Q after 5 × 10⁻⁴ s. ii is true, so the answer is i and ii.
• c ii and iii: iii fails, and i cannot be left out: x² = 2as = 2 × 4 × 10⁵ × 0.0405 = 32400, so x = 180 ms⁻¹. The answer is i and ii.
• d i, ii and iii: iii fails: P takes 4.5 × 10⁻⁴ s to stop from 180 ms⁻¹ and Q takes 5 × 10⁻⁴ s from 200 ms⁻¹. The answer is i and ii.