12) This problem is a continuation of problem 11. The object described is moved by a 12 Newton net force across a horizontal surface. We need to find the kinetic energy of the object at the end of the 5-second interval.
We already know the velocity at time t = 5 seconds from our work in problem 11. We could very easily solve this problem through plugging in our velocity from problem 11; however, we want to refrain from doing so because if we got problem 11 wrong, it would lead to getting problem 12 wrong as well.
Let's start with a definition of the final kinetic energy.
You may remember our proof in problem 11 of the Impulse-Momentum theorem. You may get the intuition that we can use this to replace the product m*v[f].
If we substitute this in for m*v[f], we can see that this equation includes only given values. We have found a clever way to solve this question and avoid depending on our answer to question 11.
Answer: B
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