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Home Q & A Board Science-Related Homework Help Physics
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venous360 venous360
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9 years ago
1): In a museum exhibit of a simple pendulum, a very small but dense 6.0-kg ball swings from a very light 2.5-m wire. The ball is released from rest when the pendulum wire makes a 65° angle with the vertical, and it swings in a circular arc with no appreciable friction or air resistance. What is the tension in the wire just as the ball swings through its lowest position?
 A. 59 N  
 B.  68 N  
 C.  11 N  
 D.  0 N  
 E. 130 N  


2):A 3.0-kg brick rests on a perfectly smooth ramp inclined at 34° above the horizontal. The brick is kept from sliding down the plane by an ideal spring that is aligned with the surface and attached to a wall above the brick. The spring has a spring constant (force constant) of 120 N/m. By how much does the spring stretch with the brick attached?
 
A. 24 cm  
B.360 cm  
C.14 cm  
D.  240 cm  
E. 36 cm  
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nmaredia11nmaredia11
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9 years ago Edited: A year ago, bio_man
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#2
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9 years ago
we have sin25= 2,5-x/2,5 <=> 0,42*2,5 = 2,5-x <=> x=1,45m

So, the energy of the ball is m*g*h=87j
This is equal to the kinetic energy at the lowest point: K=1/2*m*u2 <=> 87=3*u2 <=> u2=29 u=5,4

The tension equals the centripetal force: F=m*u2/r=6*29/2,5= 69.6N
(again it's like before, or I made some mistake? I'm kidda tired and I don't know)
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venous360 Author
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#3
9 years ago
Thank you so much for trying Slight Smile this helps a lot.
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