Answer:
The force exerted on an electron is 
Explanation:
Given that,
Charge = 3 μC
Radius a=1 m
Distance = 5 m
We need to calculate the electric field at any point on the axis of a charged ring
Using formula of electric field


Put the value into the formula


Using formula of electric field again

Put the value into the formula


We need to calculate the resultant electric field
Using formula of electric field

Put the value into the formula


We need to calculate the force exerted on an electron
Using formula of electric field


Put the value into the formula


Hence, The force exerted on an electron is 
Answer:
the mass of the body is 0.02 kg.
Explanation:
Given;
relative density of the oil,
= 0.875
mass of the object in oil,
= 0.013 kg
mass of the object in water,
= 0.012 kg
let the mass of the object in air = 
weight of the oil, 
weight of the water, 
The relative density of the oil is given as;

Therefore, the mass of the body is 0.02 kg.
Depends on who and where I’m just answering