In electrostatics problems, you are usually not given forces directly. Instead, you must first draw the...

 

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In electrostatics problems, you are usually not given forces directly. Instead, you must first draw the charges on a coordinate system, then use Coulomb's Law to find the magnitudes and sketch the directions of the forces. After you do that, then it is a math problem of vector addition. Question 7: Charge Q = +2.00 C is at the origin and Q = +3.50C is on the x-axis at x = -50.0cm Find the magnitude of the net force on charge Q3 = +1.50C. Q3 is on the y-axis at y = 120.0cm PLAN: (a) Draw a coordinate system, sketch the charges, and at Q3, sketch vector F (the force Q3 experiences due to Q), vector F2 (the force Q3 experiences due to Q2) and the net vector F = F + F2. *Notice the notation is simplified from what we used previously: F = F31, F2 = F32 (b) Use Coulomb's Law to find F and F2. What is r in Coulomb's Law? Use the coordinates of the charges, or look on your diagram to find r (the distance between Qand Q3) and r2 (the distance between Qand Q3). (c) Find the components of F and F2: Fix Fly F2x Fzy (d) Add x components: Fx = Fix + F2x (e) Add y components: Fy = Fy + F2y (f) Find the magnitude, F = F2+F2 In electrostatics problems, you are usually not given forces directly. Instead, you must first draw the charges on a coordinate system, then use Coulomb's Law to find the magnitudes and sketch the directions of the forces. After you do that, then it is a math problem of vector addition. Question 7: Charge Q = +2.00 C is at the origin and Q = +3.50C is on the x-axis at x = -50.0cm Find the magnitude of the net force on charge Q3 = +1.50C. Q3 is on the y-axis at y = 120.0cm PLAN: (a) Draw a coordinate system, sketch the charges, and at Q3, sketch vector F (the force Q3 experiences due to Q), vector F2 (the force Q3 experiences due to Q2) and the net vector F = F + F2. *Notice the notation is simplified from what we used previously: F = F31, F2 = F32 (b) Use Coulomb's Law to find F and F2. What is r in Coulomb's Law? Use the coordinates of the charges, or look on your diagram to find r (the distance between Qand Q3) and r2 (the distance between Qand Q3). (c) Find the components of F and F2: Fix Fly F2x Fzy (d) Add x components: Fx = Fix + F2x (e) Add y components: Fy = Fy + F2y (f) Find the magnitude, F = F2+F2