Potential energy of an object

  • #1
1,197
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The potential energy of an object is given by U(x)=0.5kx^2+3kx, where U is joules, x is in meters and k is a constant. What is the force acting on the object when x=0?

PE=Fd
0.5kx^2+3kx=Fd
0.5kx+3k=F
F=3k

The answer is -3k, why?
 

Answers and Replies

  • #2
13
0
Recall Work = -(delta)PE

Fd = -(0.5kx^2 + 3kx)
F = -0.5kx - 3k
F = -3k , x = 0
 
  • #3
1,197
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what is work for KE?

W=.5mv^2
or
W=-.5mv^2
 
  • #4
Doc Al
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The relationship between the potential function and the force is this: [itex]F = - dU/dx[/itex].
 
  • #5
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would the object's Kinetic energy be positive then?
 
  • #6
Doc Al
Mentor
45,140
1,443
UrbanXrisis said:
would the object's Kinetic energy be positive then?
Beats me. That depends on the total mechanical energy, which you have not specified.
 

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