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6. A stone is thrown vertically upward with a velocity of 30 m/s. How high will it rise? After how much time will it return to ground?Ans. 45 m, 6s |
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Answer» - Height Time taken to return to ground • Given:-Stone is thrown vertically upwards with velocity [u] = 30 m/s• To Find:-1. Height to which it will rise2. Time taken to return to ground• Solution:-CASE 1: • Using 3rd EQUATION of motion:-here,v = 0u = 30 m/sg = - 10 m/s² [as stone is thrown vertically upwards i.e OPPOSITE to gravity]h = ?Now,→ (0)² - (30)² = 2 (-10) h→ 0 - 900 = -20 h→ h = → Case 2:• Using 1st Equation of motion:-→ → 0 = 30 + (-10)t→ 0 = 30 - 10 t→ -30 = -10 t → t = → t = 3 sec.Therefore,time taken to reach the maximum height will be 3 sec.• Time taken to return to the ground will be 2 × 3 sec.= 6 sec.→ |
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