Which of the following is correct?

Correct answer: c v² = 2as

With u = 0, v² = u² + 2as gives v² = 2as, the book's formula for motion that starts from rest.

Why the other options are wrong

• a v = st: v = st makes velocity the product of distance and time. Velocity = distance/time, so s = vt.
• b s = ut + 1/2 at: s = ut + 1/2 at lacks the square on t, so the dimensions do not match. The correct formula is s = ut + ½at².
• d t = ((u + v)/2) S: s = ((u + v)/2)t, so t = s ÷ ((u + v)/2). Here it is multiplied instead, so the dimensions do not match.