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How long does it take to reach its highest point? Answer in units of s. What is...

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juniormax | Student, Undergraduate | eNotes Newbie

Posted September 29, 2009 at 9:36 PM via web

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How long does it take to reach its highest point? Answer in units of s. What is velocity when it returns to the level from which it started? ans. m/s

A ball is thrown vertically upward with a speed of 26.3 m/s.

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krishna-agrawala | College Teacher | Valedictorian

Posted September 29, 2009 at 9:56 PM (Answer #1)

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The ball reaches its highest point when the velocity becomes 0 under the influence of gravity.

Therefore time taken to reach highest point = (initial velocity)/acceleration

= 26.3/9.81 = 2.6809 seconds.

The velocity when it returns to the original is point is exactly equal and opposite of initial velocity.

Thus velocity when ball returns to starting point = -26.3 m/s

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neela | High School Teacher | Valedictorian

Posted September 29, 2009 at 10:00 PM (Answer #2)

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The equation for the velocity for the ball thrown vertically :

v= u+at, where u is the initial velocity a is the retardartion due gravitional acceleration, and t is the time of the motion.

At the highest point the velocity v of the ball is zero.

Therefore, 0=26.3-9.8t or 9.8t=26.3. Therefore, t= 26.3/9.8=2.6837 is the time to reach the heighest point.

The height reached s= ut-(1/2)gt^2 = 26.3(26837)-(1/2)(9.8)(2.6837^2)=35.2903m

Returning tothe ground:

Initial velocity u= 0, final velocity v to be found and acceleraion is the acceleration due to gravitation.The height s=35.2903m

We know that v^2-u^2= 2as

v= sqrt(2as)= sqrt(2*9.8*35.2903)=26.3 m/s towards the earth. It is equival in magnitude to the starting velocity but opposite in direction.

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