Question

A ball is thrown vertically upward with a velocity of \(5 \, \text{m/s}\); if it takes 10 sec for the upward journey, how long does the downward journey take?

• A. \(5 \, \text{s}\)
• B. \(10 \, \text{s}\)
• C. \(15 \, \text{s}\)
• D. \(20 \, \text{s}\)

Hint:

For vertical motion:
\textbf{Time up = Time down} (if same starting and ending level).

Answer 1

The Correct Option is B

Concept: In vertical motion under gravity (neglecting air resistance), the time taken to go up is equal to the time taken to come down to the same level.
Step 1: Understanding the motion.
The ball is projected upward and returns back under the influence of gravity. The motion is symmetric.
Step 2: Using symmetry of motion.
Time of ascent = Time of descent (for same height).
Step 3: Apply given data.
Upward journey time = \(10 \, \text{s}\) \[ \Rightarrow \text{Downward journey time} = 10 \, \text{s} \]
Conclusion:
Thus, the downward journey also takes \( \boxed{10 \, \text{s}} \).