ball thrown up w/ height above cliff base s=-16t^2+96t+144  TOPIC_SOLVED

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ball thrown up w/ height above cliff base s=-16t^2+96t+144

Postby cpoolrn on Thu Apr 08, 2010 9:22 pm

A ball is thrown directly upward from the edge of a cliff in wuch a way that t seconds later, it is

s=-16t^2+96t+144

feet above the ground at the base of the cliff. Sketch the graph of this equation (making the t-axis the horizontal axis) and then answer these questions:

a. How high is the cliff?
b. When (to the nearest tenth of a second) does the ball hit the ground at the base of the cliff?
c. Estimate the time it takes for the ball to reach its maximum height. What is the maximum height?
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Postby stapel_eliz on Fri Apr 09, 2010 10:49 am

From another post you made, you're in calculus. But this question on requires stuff you learned back in algebra.

cpoolrn wrote:A ball is thrown directly upward from the edge of a cliff in wuch a way that t seconds later, it is

s=-16t^2+96t+144

feet above the ground at the base of the cliff. Sketch the graph of this equation (making the t-axis the horizontal axis) and then answer these questions:

a. How high is the cliff?

At what time is the ball right at the cliff top? Plug that time value in for "t" and find the height.

cpoolrn wrote:b. When (to the nearest tenth of a second) does the ball hit the ground at the base of the cliff?

When the ball hits the ground at the base, what is its height above the base? Plug this value in for "s" and solve for the time "t".

cpoolrn wrote:c. Estimate the time it takes for the ball to reach its maximum height. What is the maximum height?

I'm not sure what they mean by "estimate" here...? But the maximizing values will be at the vertex, so find the vertex (by completing the square or else using the formula) and provide the value of the height. :wink:
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Re: ball thrown up w/ height above cliff base s=-16t^2+96t+1

Postby cpoolrn on Fri Apr 09, 2010 5:51 pm

The question doesn't provide any values to plug into the equation. I am wondering if they are asking for me to set up the equations that will answer the questions, instead of the actual answer. I am taking the course through TTU by correspondance and I don't have an actual instructor to ask questions. I am running out of time to complete the course and wish, now, that I hadn't signed up for this course via correspondence. I appreciate your input.
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  TOPIC_SOLVED

Postby stapel_eliz on Fri Apr 09, 2010 9:15 pm

You are expected to use logic and real-world knowledge. For instance, if one starts the time count when the ball is tossed upward from the top of the cliff, then what is the time when the ball is at the top of the cliff? You plug that value in, and simplify to find the answer.
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