SUVAT Sign أخطاء That Flip Your الإجابة

Constant-التسارع equations only شغل if you pick one positive direction and stick to it. These traps show where signs usually go wrong.

v = u + at · s = ut + ½at² · v² = u² + 2as — Pick one positive axis for the whole problem

فخ 1: Treating every slowdown as “a is negative” without a defined axis

خطأ: Car slows from 20 m/s to 10 m/s → student writes a = −5 without saying which way is positive.

صحيح: If forward is positive and the car slows while moving forward, a is negative. State the axis first.

التصحيح: Negative التسارع means سرعة متجهة is becoming less positive — not always “going backward.”

خطأ: Walk 4 m forward and 1 m back → put s = 5 m into SUVAT.

صحيح: الإزاحة is net change: s = +3 m if forward is positive. المسافة traveled is 5 m.

التصحيح: SUVAT uses الإزاحة s, not total path length.

خطأ: u = +12, a = −3, s = +16 → computing as if everything were positive magnitudes only.

صحيح: Keep signed values: v² = (12)² + 2(−3)(16) = 144 − 96 = 48 → |v| = √48.

التصحيح: Square roots give ±v; the sign of v comes from the physical direction you chose.

خطأ: Taking up as positive for u but down as positive for g في the same line.

صحيح: If up is positive, g ≈ −9.8 m/s². If down is positive, g ≈ +9.8 m/s². One choice only.

التصحيح: اكتب “up positive” or “down positive” at the top of the شغلing.

خطأ: Known u, v, t — but using s = ut + ½at² without finding a first (or picking the equation that omits a).

صحيح: استخدم s = ½(u + v)t when a is unknown, or find a = (v − u)/t first.

التصحيح: List knowns, then pick the equation that does not need the missing symbol.

اختر one positive direction, write it down, and keep every u, v, a, and s consistent with that choice.

No. It means سرعة متجهة is decreasing along your positive axis. The جسم can still be moving forward while slowing down.

No. الإزاحة is net position change (signed). المسافة is path length (≥ 0).