एक गेंद को (20 m/s) की चाल से ऊपर फेंका गया। उसकी ऊँचाई \(h=20t-5t^2\) है। गेंद (15 m) ऊँचाई पर किस समय होगी?
A ball is thrown upward with speed (20 m/s\(). Its height is (h=20t-5t^2). At what times will it be at height (15\) m)?
Explanation opens after your attempt
A. (1 s) और (3 s)(1 s) and (3 s)
Concept
From \(20t-5t^2=15\), we get \(t^2-4t+3=0\). Hence (t=1) and (t=3), representing upward and downward motion.
Why this answer is correct
The correct answer is A. (1 s) और (3 s) / (1 s) and (3 s\(). From (20t-5t^2=15), we get (t^2-4t+3=0). Hence (t=1) and (t=3), representing upward and downward motion.\)
Exam Tip
\(20t-5t^2=15\) से \(t^2-4t+3=0\)। इसलिए (t=1) और (t=3), जो ऊपर जाते और नीचे आते समय हैं।
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