Question

A body falls from rest. In the last second of its fall it covers half of the total distance. If g is $ 9.8\text{ }m/{{s}^{2}}, $ then the total time of its falls is (in second)

• A. 2
• B. $ 2+\sqrt{2} $
• C. $ 4-\sqrt{2} $
• D. 3

Answer 1

Answer: (B)

According to equation $ h=\frac{1}{2}g{{t}^{2}} $
$ \frac{h}{2}=\frac{1}{2}g{{(t-1)}^{2}} $
Solving Eqs. (i) and (ii), we get
$ t=2\pm \sqrt{2}s $
$ t=2+\sqrt{2}s $