Question

A stone dropped from the top of a tower reaches ground in 4 s. Height of the tower is $(g = 10 \, m/s^2)$

• A. 20 m
• B. 40 m
• C. 60 m
• D. 80 m

Answer 1

Answer: (D)

80 m

Answer 2

As, $h = ut + \frac{1}{2} gt^2$
Here, $u = 0 , g = 10 \, m \, s^{-2} , t = 4\,s$
$\therefore \:\:\:\: h = 0 \times 4 + \frac{1}{2} \times 10 \times 4^2 = 80 \, m$