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Q90 (NDA-II/2021) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Basic mechanics concepts

A tennis ball is thrown in the vertically upward direction and the ball attains a maximum height of 20 m. The ball was thrown approximately with an upward velocity of

Result
Your answer: —  Â·  Correct: D
Explanation

To find the initial upward velocity of a tennis ball reaching a maximum height of 20 m, we use the kinematic equation for vertical motion: v² = u² - 2gh [1]. At the maximum height, the final vertical velocity (v) is 0 m/s [1]. Using the standard value for acceleration due to gravity (g) as approximately 10 m/s² for simplicity in competitive exams, the equation becomes 0 = u² - 2(10)(20). Solving for u gives u² = 400, which results in an initial velocity (u) of 20 m/s. If using the more precise value of g = 9.8 m/s², the calculation yields u = √(2 * 9.8 * 20) = √392 ≈ 19.8 m/s. In both cases, the value is approximately 20 m/s, making option 4 the correct choice.

Sources

  1. [1] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 5: Exploring Forces > Activity 5.8: Let us observe > p. 72
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