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Question: A ball is thrown vertically upwards from the top of a tower at \(4.9ms^{- 1}\). It strikes the pond ...

A ball is thrown vertically upwards from the top of a tower at 4.9ms−14.9ms^{- 1}. It strikes the pond near the base of the tower after 3 seconds. The height of the tower is

A

73.5 m

B

44.1 m

C

29.4 m

D

None of these

Answer

29.4 m

Explanation

Solution

h=ut+12gt2, 6mut=3 6musec, 6muu=−4.9 6mum/sh = ut + \frac{1}{2}gt^{2},\mspace{6mu} t = 3\mspace{6mu}{sec,}\mspace{6mu} u = - 4.9\mspace{6mu} m/s

⇒h=−4.9×3+4.9×9=29.4 6mum\Rightarrow h = - 4.9 \times 3 + 4.9 \times 9 = 29.4\mspace{6mu} m