Science:Math Exam Resources/Courses/MATH110/December 2015/Question 05 (c)
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Question 05 (c) 

A ball is floating on the surface of the sea. The ball’s height (in m) above the sea floor at time (in s) is given by Answer the questions below. Evaluate all function values and provide justification for your claims. Include units. (c) Is the ball moving up or down at ? Explain. 
Make sure you understand the problem fully: What is the question asking you to do? Are there specific conditions or constraints that you should take note of? How will you know if your answer is correct from your work only? Can you rephrase the question in your own words in a way that makes sense to you? 
If you are stuck, check the hint below. Consider it for a while. Does it give you a new idea on how to approach the problem? If so, try it! 
Hint 

When a ball is moving up, it means that is increasing. On the other hand, when a ball is moving down, it corresponds that is decreasing. Recall that when on , is increasing on the interval. 
Checking a solution serves two purposes: helping you if, after having used the hint, you still are stuck on the problem; or if you have solved the problem and would like to check your work.

Solution 

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Please rate my easiness! It's quick and helps everyone guide their studies. According to the Hint, it is enough to check the sign of at . From the part (b), we have , and therefore, is increasing at . Answer : 