Phys Sample Quiz 1 soln

Phys Sample Quiz 1 soln - Question 1 Three charges , +q,...

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Question 1 Three charges , +q, +2q, +4q are connected by strings as shown in the diagram. Find the tensions T 1 and T 2 The tension in the string is equal to the sum of the repulsive forces on the charge from the other two charges For charge +q By Coulomb’s law Force due to charge 2q = k.q.2q/d 2 =2kq 2 /d 2 Force due to charge 4q = k.q.4q/(2d) 2 = kq 2 /d 2 Total Force = T 1 = 2kq 2 /d 2 + kq 2 /d 2 = 3kq 2 /d 2 For charge +4q Force due to charge 2q = k.4q.2q/d 2 = 8kq 2 /d 2 Force due to charge q = k.4q.q/(2d) 2 =kq 2 /d 2 Total Force = T 2 = 9kq 2 /d 2 Suggested Marking scheme Statement of method, diagram etc 7 For charge +q Force due to 2q 3 Force due to 4q 3 Total force 3 Same for charge 4q 9 +q +2q +4q T 1 T 2 d d

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Question 2 A thin uniformly charged rod with a total charge of 6 µ C and length 25 cm is placed along the y axis, centered at the origin. A point charge of 1 µ C is placed at (x,y)=(1cm,0cm). What is the electrostatic force on a 10 µ C charge at position (6cm,0cm)? Those that calculate the
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This note was uploaded on 10/07/2009 for the course PHYS 1302W taught by Professor Marshak during the Spring '08 term at Minnesota.

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Phys Sample Quiz 1 soln - Question 1 Three charges , +q,...

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