A bird flies at 10ms\(^{-1}\) for 3s, 15ms\(^{-1}\) for 3s and 20 ms\(^{-1}\) for 4s. Calculate the bird's average speed
4.5 ms-1
15.0 ms-1
15.5 ms-1
51.7 ms-1
Correct answer is C
Av. speed = \(\frac{3 \times 15 + 3 \times 10 + 4 \times 20}{3 + 3 + 4}\)
= 15.5 ms\(^{-1}\)