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A T-ball player hits a ball from a tee that is 0.6m tall. The height of the ball at a...

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topgun13 | (Level 2) Honors

Posted November 15, 2011 at 9:11 AM via web

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A T-ball player hits a ball from a tee that is 0.6m tall. The height of the ball at a given time is modelled by the function `h(t)=-4.9t^2+7t+0.6` .

where height, h(t) is in metres and time, t, is in seconds.

A) What will the height be after 1s?

b) When will the ball hit the ground?

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hala718 | High School Teacher | (Level 1) Educator Emeritus

Posted November 15, 2011 at 9:45 AM (Answer #1)

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`h(t)= -4.9t^2 + 7t +0.6`

`` a) we need to find the height of the ball after t= 1 second.

We will substitute with t= 1.

==> h(1)= -4.9(1) + 7(1)+ 0.6 = 2.7 m

Then the height after 1 second is 2.7 meters.

 

b)When will the ball hit the ground.

When the ball hit the ground then the height h= 0.

==> `h(t)= -4.9t^2 + 7t + 0.6 = 0 `

`==gt -4.9t^2 + 7t + 0.6 = 0`

Now we will solve for t.

==>`t1= (-7+sqrt(49+4*0.6*4.9))/(2*-4.9) = (-7+7.7949)/(-9.8)= -0.0811 ( Not valid) `

`==gt t2= (-7-7.7974)/(-9.8) = 1.9143` seconds.

Then the time for the ball to hit the ground is 1.9143 seconds.

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