Quick answer: For straight-line motion with constant acceleration: v = u + at, s = ut + at²/2, and v² = u² + 2as. Choose a positive direction and use signed velocity, acceleration and displacement.
Worked example
A body starts from rest and accelerates at 2 m/s² for 5 s. Find final velocity and displacement.
- u = 0, a = 2, t = 5.
- v = 0 + 2×5 = 10 m/s.
- s = 0×5 + (1/2)×2×25 = 25 m.
Check the result
Average velocity under constant acceleration is (u + v)/2 = 5 m/s; multiplying by 5 s gives 25 m.
Stuck on a question? Ask it here and get a step-by-step answer in seconds — pay only per answer, no subscription. Ask your doubt now →
Common mistake to avoid
Do not use these equations for variable acceleration without justification. Braking acceleration is negative if forward motion is positive.
Try it yourself
1. u = 10 m/s, a = −2 m/s², t = 3 s: find v. 2. Find displacement over those 3 s.
Answers and reasoning
1. v = 10 − 6 = 4 m/s. 2. s = 30 − 9 = 21 m; the body has not yet reversed direction.
Need help with your own attempt? Ask a study question. AI answers require an account and paid credits. Check important steps with your textbook or teacher.
Stuck on a question? Ask it here and get a step-by-step answer in seconds — pay only per answer, no subscription. Ask your doubt now →