TBR physics Passage 4 question 27

[2010premed]

This is a projectile problem, but the starting height is higher than the ending height. the questions says "which of the following graphs best depicts the relationship between launch angle and range in the experiment?"

There are two choices that show that the longest range happens at angle as 45 degrees, and the answer book says that they should be eliminated b/c the start and end point are not equal. Then there's a graph that shows the longest range is at less than 45 and the other that it is at greater than 45 degrees... HELP

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[2010premed]

Nevermind, I see it... of course there's longer range with an angle of less than 45 degrees (when the initial and final heights are not equal)

 

[VooDooo327]

45 degrees will always get the best range given the beginning and ending heights are the same. The book is right in eliminating those choices since in the question the heights are not. Since the ending height is lower to achieve the best range you lower the angle. The lower ending height compensates for the lower range. So, it acts like you are throwing it at 45 degrees on an even surface.

 

[2010premed]

Thanks! So would it be different if the end height was higher than the beg height?

 

[VooDooo327]

Yeah you want the angle to be more than 45 degrees. Think of it like this: If you were trying to throw something on top of a building. You need the extra angle to just get it up there.

 

[2010premed]

Thanks!

 

[Danlee07]

zero launch: less than 45
same: 45
final is higher: more than 45