MATH 2374 Midterm: MATH 2374 UMN Spring 10 Exam 2sol
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Second midterm: solutions: an e ective way to solve this problem is to employ the product rule formula 1 div (f curl g) = f div g + f g. In our case, take g to be equal to curl f. But the brute force approach still works pretty well here: i. =(cid:0)3y2zx 0(cid:1) i (cid:0)y3z 4xz(cid:1) j + (0 0) k. = 3y2zx i + (4xz y3z) j f curl f = (z + 1)5 3y2zx i + (z + 1)5 (4xz y3z) j. = (z + 1)5 3y2z + ( 3y2z) + 0 = 0. div (f curl f) = Y(cid:16)(z + 1)5 (4xz y3z)(cid:17) + Y(cid:16)0(cid:17: the work done by the force eld f in moving a particle along the path c is equal to the line integral. In our case, in order to set up this integral, we need to gure out rst, what force eld is acting on the particle.