A stone is thrown horizontally with initial velocity 15m/s from a tower 20 m high. How long does it take to reach the ground? [g= 10m/s\(^2\)
A
2s
B
4s
C
5s
D
1s
Verified Correct Answer: A.
Physical Principles & Numerical Solution
\(h = \frac{1}{2} g t^2\), at max height v = 0m/s
Given: h = 20m, g = 10 ms\(^2\)
Rearranging:
\(t^2 = \frac{2h}{g} = \frac{2 \times 20}{10} = 4\)
\(t = \sqrt{4}\) = 2s
Thus, the time to reach the ground is: t = 2s
Source: Myschool Past Questions Archive (Record #62308)