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Centripital forces Question

  • Thread starter mike_302
  • Start date
  • #1
103
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Homework Statement


1. a) Determine the speed required by a coaster that would cause a rider to experience a normal force of 2mg at the top of a clothoid loop where the radius is 12meters.


Homework Equations





The Attempt at a Solution



http://i160.photobucket.com/albums/t161/mike_302/physicsq.jpg [Broken]

That is my attempt at aa solution. Now, the only problem is that I get a square root negative... Obviously imaginary. Can't do it. But if I made the number positive, I get the right value of 19m/s for speed.

Somewhere/somehow, I need to cancel out the negative in there. Can someone explain how?

Thanks!
 
Last edited by a moderator:

Answers and Replies

  • #2
Doc Al
Mentor
44,877
1,129
Hint: In which direction is the coaster's acceleration? Is that positive or negative?
 
  • #3
103
0
oh! okay. so acceleration is down. GOT IT! WOW! HUGE thanks!
 

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