Kinematic equation for constant acceleration

Steps:

• Start with the definition of acceleration: a = (v - u)/t.
• Rearrange to solve for initial velocity: u = v - at.
• This relates initial velocity u, final velocity v, acceleration a, and time t.
• Verify by substituting: if t=0, u=v, which holds.

Why B is correct:

• It directly follows from the acceleration definition a = (v - u)/t, rearranged to express u in terms of v, a, and t.

Why the others are wrong:

• A is identical to B, so not uniquely wrong but listed separately.
• C rearranges B to v = u + at, which is equivalent but not the exact form asked.
• D incorrectly uses at² instead of at, confusing velocity with displacement equation s = ut + (1/2)at².

Final answer: B