Physics Question

[BrianK0220]

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tan theta = y/x = 3 and theta equals 72 degrees.

How are you supposed to come up with 72 degrees without a calculator?

 

[Rabolisk]

You are not.

 

[FrkyBgStok]

if you are looking at a mcat prep book, get a different one. if you are asking in general based on your physics class, get an mcat prep book.

 

[BrianK0220]

Thanks guys. I was reading the kinematics notes in the kaplan premier program 2008-2009 edition.

 

[jmart]

I think I have four or five sets of Kaplan books. I think it was last year that they finally did a big overhaul and updated the books. Now the practice questions are formulated in MCAT form.

 

[BerkReviewTeach]

tan theta = y/x = 3 and theta equals 72 degrees.

How are you supposed to come up with 72 degrees without a calculator?

You won't necessarily have to know that, but you could get a question like this.

• In the experiment, it was observed that Material VI had an average threshold angle 72 degrees. We find that mustatic is equal to the tangent of the threshold angle. What is the approximate mustatic for Material VI against the ramp?
  
  a) 0.50
  b) 0.86
  c) 1.16
  d) 3.00

Knowing the exact tangent is pointless, but being able to deduce the approximate tangent (to eliminate the wrong answers) is helpful. Tangent = sin/cos, so for the three common angles you should know that tan 30degrees = 0.5/0.86, tan 45degrees = 0.71/0.71, and tan 60degrees = 0.86/0.5. Solving for tan 60degrees, we get 1.72. For an angle greater than 60degrees, the tangent will be larger than 1.72. Only choice D fits that restriction, so it must be the answer.

So while knowing the exact value of tangent 72degrees is fruitless, knowing that it is greater than 1.72 and being able to think through a multiple choice question is helpful. If you don't like the way a question is worded (i.e., think that it's unrealistic), then rewrite your own question using the information in a more applicable way.