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How fast must a ball be thrown upward to reach a height of 12 m?

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gretjxfj | Student, Undergraduate | (Level 1) Honors

Posted February 26, 2012 at 7:37 PM via web

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How fast must a ball be thrown upward to reach a height of 12 m?

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justaguide | College Teacher | (Level 2) Distinguished Educator

Posted February 26, 2012 at 9:34 PM (Answer #1)

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When a ball is thrown vertically upwards, there is an acceleration acting on it due to the gravitational force of attraction of the Earth equal to 9.8 m/s^2. This acts in a direction vertically downwards.

Let the magnitude of velocity required to throw the ball upwards to a height of 12 m be equal to V.

At the highest point, the velocity of the ball is equal to 0. Use the relation v^2 - u^2 = 2*a*s where v is the final velocity, u is the initial velocity, a is the acceleration and s is the distance traveled. This gives:

0^2 - V^2 = 2*(-9.8)*12

=> V^2 = 24*9.8

=> V^2 = 235.2

=> V = sqrt 235.2

=> V = 15.33

The velocity with which a ball must be thrown vertically upwards so that it reaches a height of 12 m is approximately 15.33 m/s.

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