Personal space differs from culture to culture, though it is widely acknowledged that Europe and U.S have bigger personal space requirements that their counterparts in Asia.
Hakeem might not realize it but it’s commonly accepted for Americans to have a distance between four to twelve feet between one another in social settings, especially in professional ones. A distance of two feet is only acceptable if the individual is part of the person’s inner circle, such as friends and family.
Answer: 
Explanation:
Given
The velocities of the protons are 400 m/s and 450 m/s
Mass of the Proton is 
Since they travel in the opposite direction, therefore, their momentum cancels out each other.
Momentum is the product of mass and velocity

The direction of momentum is in the direction of proton having 450 m/s velocity.
It burns when you start your car and that conducts electricity which burns it.