WAEC Physics 2016 Paper

Concept:At terminal velocity, the falling object moves with constant speed because forces balance.Explanation:When the ball is dropped, gravity pulls it downward while air resistance acts upward.As speed increases, air resistance also increases.Terminal velocity is reached when air resistance equals the weight of the ball.At this point, the net force on the ball is zero: $F_{\text{net}} = mg - F_{\text{air}} = 0$From Newton's second law, if net force is zero, acceleration is also zero:$a = \frac{F_{\text{net}}}{m} = 0$So statement i is correct: acceleration is zero.Statement ii is correct: net force is zero.Statement iii is incorrect: velocity does not increase; it becomes constant at terminal velocity.Answer:B. i and ii only