Problem
A person on top of a \( 55 \mathrm{~m} \) tall building drops a rock. How long (second unit)will it take for the rock to reach the ground
Solution
Step 1 ：\( h = 55 \mathrm{~m}, g = 9.8 \mathrm{~m/s^2} \)
Step 2 ：\( t = \sqrt{\frac{2h}{g}} \)
Step 3 ：\( t = \sqrt{\frac{2 \times 55}{9.8}} \approx 3.3623 \mathrm{~s} \)
