Problem 25.41 What is the tension in the string? Express your answer using two s

Question

Problem 25.41 What is the tension in the string? Express your answer using two significant figures. Two small metal cubes with masses 2.0 g and 4.0 g are tied together by a 5.5-cm-long massless string and are at rest on a frictionless surface. Each is charged to +2.0 C T= 12 N Submit My Answers Give Up Correct Significant Figures Feedback: Your answer 11.9 N was either rounded differently or used a different number of significant figures than required for this part Part C The string is cut. What is the speed of each sphere when they are far apart? Hint: There are two conserved quantities. Make use of both Express your answers using two significant figures. Enter your answers numerically separated by a comma U2 m/s Submit My Answers Give Up Incorrect; Try Again; 7 attempts remaining; no points deducted Provide Feedback Continue

Explanation / Answer

c) The charges separate with an elec. PE = ½ E each

E = [9 X 109 X (2 X 10-6)2]/ 0.055= 0.65 J

Assuming at a large separation their mutual repelling forces have transferred all the original EPE to KE, their velocity is given by

Hence

0.5 E = 0.5 mv2

v2 = E/m

For the 0.002kg sphere, v2 = 0.65 / 0.002 => v = 18.1 m/s

For the 0.004kg sphere, v² = 0.65 / 0.004 => v = 12.79 m/s (opposite direction)

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