A stone is dropped from a height of 45m. Find the time it takes to hit the ground. \([g = 10 ms^{-2}]\)
-
3.0 seconds
- 4.5 seconds
- 5.0 seconds
- 9.0 seconds
The correct answer is: A
Explanation
\(s = ut + \frac{1}{2}gt^{2}\)
\(u = 0; s = 45m; g = 10ms^{-2}\)
\(45 = 0 + \frac{1}{2}(10)t^{2} = 5t^{2}\)
\(t^{2} = \frac{45}{5} = 9\)
\(t = 3.0s\)