Problem 25.80 Part A If the beads are released from rest, what is the speed VC o

Question

Problem 25.80 Part A If the beads are released from rest, what is the speed VC of C at the instant the beads collide? Two 1.5-mm-diameter beads, C and D, are 12 mm apart, measured between their centers. Bead Chas mass 1.0 g and charge 2.5 nC. Bead D has mass 17g and charge -1.0 nC. Express your answer to two significant figures and include the appropriate units. 'H WA the r CO o ) ? vc Value Units Submit my answers Give Up Part B What is the speed up of D at the instant the beads collide? Express your answer to two significant figures and include the appropriate units. 'H A Ho ODol ? VD = Value Units Submit My Answers Give Up Provide Feedback Continue

Explanation / Answer

Applying momentum conservation,

1 vC = 1.7 vD

vC = 1.7 vD .....(i)

Applying energy conservation,

PEi + KEi = PEf+ KEf

k q1 q2 / r1 + 0 = k q1 q2 / r2 + mC vC^2 /2 + mD vD^2 / 2

(9 x 10^9)(2.5 x 10^-9)(1 x 10^-9)[1 / (0.0015) - 1 / 0.012] = (1 x 10^-3) (1.7vD)^2 /2 + (1.7 x 10^-3)(vD^2) /2

1.3125 x 10^-5 = 2.295 x 10^-3 vD^2

vD = 0.0756 m/s ..........Ans(B)

vC = 0.129 m/s ........Ans(A)

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