The U of a 4kg object is given by U= 3x^2-x^3 for x smaller than or equal to 3. U is equal to 0 for all numbers larger than 3. If the total energy of the object is 12J what is its speed at 2 meters?
K(x)=E-u(x) E=mechanical energy
The Attempt at a Solution
It seems like i would plug 2 into the u equation and get the value of U at that particular moment, then use the E, which would be 12??? and subtract the U from it.
I ended up with the answer 2m/s but I could have sworn doing something with integrals for a problem similar to this so it seems like this would be too easy.