樓主 .. 呢o的問題 , 得閒一定要畫一個free body diagram黎研究下 ..
根據你既資料 , 物件A o係free falling時受到向下既係gravitational force (mass = mA , force=mAg) , 向上既係air resistance (但題目假設為 0 ) , 冇其他力量影響 ..
物件B既diagram同A完全相等 , mass=mB , force = mBg
Assume g=gravitational constant=10
Let a=aceleration, mA and mB = mass A and mass B
引用Newton's Second Law F=ma
Force on A = mAg = mAa
2 = 2 (a) = 10
Force on B = mBg = mBa
2 = 2 (a) = 10
所以兩個情況下acceleration相等
引力學另一條公式 : v = u + at
由於係release from rest所以 u initial velocity = 0 , 亦因此可簡化成 v=at
1. vA = aAt = 10t
2. vB = aBt = 10t
已知acceleration及time於兩情況下皆相等 , 所以任何時間 vA = vB ...
