Question

One stone is projected horizontally from a $20\, m$ high cliff with an initial speed of $10 \, ms ^{-1}$. A second stone is simultaneously dropped from that cliff. Which of the following is true?

• A. Both strike the ground with the same velocity
• B. The ball with initial speed $10 \,ms ^{-1}$ reaches the ground first
• C. Both the balls reach ground at the same time
• D. One cannot say without knowing the height of the building

Answer 1

Answer: (C)

For vertical motion, the initial speed for both the stones is same, $g$ is same, hence the time when they reach
the ground will be same. $t=\sqrt{\frac{2 h}{g}}$