Question

A mass of 4kg is to be divided into two parts and are seperated by 10 cm. The maximum force between two parts is 1) 400G 2) 100G 3) 200G 4) 50G​

Answer 1

Answer:

Step 1: Calculation of force  

Let one part of the charge be  q. Thus other part of the charge is  Q−q

From Coulomb's law:

Electrostatic force between them  F=

r

2

kq(Q−q)

​

Step 2: Condition of maximum force  

For maximum force,      

dq

dF

​

=0

∴    

dq

d

​

(

r

2

kq(Q−q)

​

)=0

Or,      

dq

d

​

(qQ−q

2

)=0

Or,      Q−2q=0            

⇒   q=

2

Q

​

Hence force between them is maximum if the two parts have equal charge Q/2 each. So, Option A is correct

Explanation: