फिजिक्स में free fall जुड़ा महत्वपूर्ण concept जब कोई ऑब्जेक्ट को किसी initial velocity से भेजा जाता है और ;उसमे लगा समय =t और जब ये वापस surface पर आता तो लगने वाला समय =t" तो क्या ग्रेविटी opposite एंड similiar में सामान समय लगाती है =t+t"/2 ले कर चलेंगे , Question 18 A ball thrown up vertically returns to the thrower after 6 s. Find (a) the velocity with which it was thrown up, (b) the maximum height it reaches, and (c) its position after 4 s. Class 9 - Science - Gravitation Page 144 Time to reach Maximum height , t = 6/2 = 3 s. v = 0 (at the maximum height ) a = - 9.8 m s-² ◆ a) Using, v = u + at, we get 0 = u - 9.8 × 3 or, u = 29.4 ms-¹ Thus, the velocity with which it was thrown up = 29.4ms-¹ ◆ b) Using, 2aS = v² - u², we get S = v²- u²/2a = 0 - 29.4 × 29.4/- 2× 9.8 = 44.1 m Thus, Maximum height it reaches = 44.1 m. ◆ c) Here, t = 4s. In 3 s, the ball reaches the maximum height an...