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A ball which is thrown vertically upwards rises to a height of 20m, calculate...1. the velocity with which the ball is thrown upwards.2. the time taken by the ball to reach the highest point (g=10m/s^-2) |
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Answer» Answer 1 . Initial VELOCITY , u = 20 m/s 2 . Time , t = 2 s Given
To Find 1 . The velocity with which the ball is thrown upwards. 2 . the time taken by the ball to reach the HIGHEST point (g=10 m/s²) Concept Used We need to use equations of motion .
Solution Height , s = 20 m Here ball is thrown vertically upwards . So , at CERTAIN height the ball will go to rest . So , FINAL velocity , v = 0 m/s Acceleration , a = g = - 10 m/s² [ Thrown against the gravity ] Now , apply 3rd equation of motion . ⇒ v² - u² = 2as ⇒ 0² - u² = 2 ( - 10 ) ( 20 ) ⇒ - u² = - 400 ⇒ u² = 400 ⇒ u = 20 m/s 1 . Initial velocity , u = 20 m/s _______________________ Use 1ST equation of motion . ⇒ v = u + at ⇒ 0 = 20 + ( - g ) t\\ ⇒ 0 = 20 - 10t ⇒ 10t = 20 ⇒ t = 2 s 2 . Time taken to reach the highest point , t = 2 s __________________________ |
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