work power energy again

The potential energy of a force field is given by U(x,y) = sin(x+y) . The force acting on the particle of mass m at (0,pi/4) is:

(A) 1

(B) root 2

(D) zero

i m usin F = -dU/dr .............but after that what shud i do??

2 Answers

F_x =-âˆ‚Uâˆ‚x = -cos(x+y) = - 1√2

F_y= -âˆ‚Uâˆ‚y = - cos(x+y) = - 1√2
F = √F_x²+F_y² = 1

F=1,same like E=-âˆ‚V/âˆ‚x

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