A man throws balls with the same speed vertically upwards one after the other at an interval of 2 seconds. What should be the speed of the throw so that more than two balls are in the sky at any time?
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A man throws balls with the same speed vertically upwards one after the other at an interval of 2 seconds. What should be the speed of the throw so that more than two balls are in the sky at any time?

G1 Physics · Accepted Answer

Step 1: Balls are launched every 2 s. To have more than two balls simultaneously in air, the first ball must remain aloft for more than 4 s. Step 2: Time of flight T=2u/g. Require 2u/g>4. Step 3: Hence u>2g≈19.6 m s⁻¹. Final answer: A.