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NEET Physics QUESTION #7302
Question 1

A person throws balls vertically upward one after another at intervals of 2 s, all with the same speed. For more than two balls to be in the air simultaneously, the throwing speed must be:

  • More than 19.6 m/s✔️
  • At least 9.8 m/s
  • Less than 19.6 m/s
  • Exactly 19.6 m/s
Correct Answer Explanation

Time of flight for one ball $= \dfrac{2u}{g}$.

For more than 2 balls in the air, a third ball is thrown before the first lands, so time of flight $> 4\text{ s}$ (two intervals of 2 s each):

$\dfrac{2u}{g} > 4 \Rightarrow u > 2g = 2 \times 9.8 = 19.6\text{ m/s}$