Question

A stone is kicked horizontally from the edge of a cliff. The stone is kicked at $7m/s$ and takes $3$ seconds to reach the ground at the base of the cliff.
Which one of the following is closest to the height of the cliff?

• A. $21meters$
• B. $45meters$
• C. $66meters$
• D. $90meters$

Answer 1

Answer: (B)

$45meters$

Time of flight $T=3$ s

Time of flight $T=\sqrt{\frac{2h}{g}}$ where $h$ is the height of the cliff

$\therefore$ $3=\sqrt{\frac{2h}{10}}$ $⟹h=45$ m