A 4.0 kg ball dropped from rest falls freely under gravity for 3.0 seconds. What speed does it attain? (g = 9.8 m/s^2)
Answer and explanation
Correct answer: D. 29.4 m/s
- Step 1: Use the free-fall equation: v = u + g*t with initial speed u = 0.
- Step 2: v = 0 + (9.8 m/s^2) * (3.0 s) = 29.4 m/s.
Answer
29.4 m/s.
Why not the others: '14.7 m/s' computes distance fallen divided by time squared; '44.1 m/s' calculates displacement (0.5 g t^2); '9.8 m/s' is the speed after only 1 second.
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