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talebone

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1. Homework Statement

Three small identical metal spheres carry electric charges, +Q, +2Q, and +3Q. The centres of the spheres lie in a straight line at fixed positions R, S and T, such that the distance between the spheres at R and S is d1 and that between the spheres at S and T is d2. Assume that the distances between the spheres is large in comparison with their size, and that the charges on the spheres act like point charges.

Q1

The sphere at S will experience a zero net electric force when d2 is equal to

A 3d1

B d1/3

C √3 d1

D d1/√3

Q2

A small metal sphere (identical to those at R, S, T) carrying a charge of-2Q is first brought into contact with the sphere at R, and then into contact with the sphere at S, and finally into contact with the sphere at T. After making contact with the three spheres, in the stated order, the charge on the sphere at T is

A +3Q

B +15Q/4

C +15Q/8

D +4Q

2. Homework Equations

F=kQ1Q2/r

3. The Attempt at a Solution

Q1 - SOLVED thanks

k(Q)(2Q)/d1

k2Q/d1

d2

d2 = √3Q d1

Q2

1. at R, the net charge will be -Q. so each sphere will have -0.5Q

2. at S, the net charge will be +1.5Q. so each sphere will have +0.75Q

3. at T, the net charge will be +3.75Q, so each sphere will have +1.875Q

which ANS C gives so I guess that's the answer. but I'm not sure why the equation is worded like that. thanks for your time :) appreciate it

Three small identical metal spheres carry electric charges, +Q, +2Q, and +3Q. The centres of the spheres lie in a straight line at fixed positions R, S and T, such that the distance between the spheres at R and S is d1 and that between the spheres at S and T is d2. Assume that the distances between the spheres is large in comparison with their size, and that the charges on the spheres act like point charges.

Q1

The sphere at S will experience a zero net electric force when d2 is equal to

A 3d1

B d1/3

C √3 d1

D d1/√3

Q2

A small metal sphere (identical to those at R, S, T) carrying a charge of-2Q is first brought into contact with the sphere at R, and then into contact with the sphere at S, and finally into contact with the sphere at T. After making contact with the three spheres, in the stated order, the charge on the sphere at T is

A +3Q

B +15Q/4

C +15Q/8

D +4Q

2. Homework Equations

F=kQ1Q2/r

^{2}3. The Attempt at a Solution

Q1 - SOLVED thanks

k(Q)(2Q)/d1

^{2}= k(2Q)(3Q)/d2^{2}k2Q/d1

^{2}= k6Q/d2^{2}d2

^{2}= k3Q(d1^{2})/k3Qd2 = √3Q d1

Q2

1. at R, the net charge will be -Q. so each sphere will have -0.5Q

2. at S, the net charge will be +1.5Q. so each sphere will have +0.75Q

3. at T, the net charge will be +3.75Q, so each sphere will have +1.875Q

which ANS C gives so I guess that's the answer. but I'm not sure why the equation is worded like that. thanks for your time :) appreciate it

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