Answer:
The electric force is 
Explanation:
From the question we are told that
The Bohr radius at ground state is 
The values of the distance between the proton and an electron 
The electric force is mathematically represented as

Where n and p are charges on a single electron and on a single proton which is mathematically represented as

and k is the coulomb's constant with a value

substituting values
![F = \frac{9*10^{9} * [(1.60*10^{-19} ]^2)}{(2.63 * 0.529 * 10^{-10})^2}](https://tex.z-dn.net/?f=F%20%3D%20%20%5Cfrac%7B9%2A10%5E%7B9%7D%20%2A%20%20%5B%281.60%2A10%5E%7B-19%7D%20%5D%5E2%29%7D%7B%282.63%20%2A%200.529%20%2A%2010%5E%7B-10%7D%29%5E2%7D)

Answer:
I = 2172.46 A
Explanation:
Given that,
The length of a solenoid, l = 2.1 m
The inner radius of the solenoid, r = 28 cm = 0.28 m
The number of turns in the wire, N = 1000
The magnetic field in the solenoid, B = 1.3 T
We need to find the current carried by it. We know that, the magnetic field in a solenoid is given by :

Put all the values,

So, it carry current of 2172.46 A.
The car's speed is 240km/4hr= 60km/hr.
There's not enough information given in the question to determine its velocity.
'Pressure' is (force) / (area).
The only choice with those units is #1 .