Reason Of Normal contact Force w.r.t. Quantum Physics

The normal force is not really due to any of the four forces of nature. The forces of nature are not all the forces in the macroscopic sense, they are just the fundamental bosonic particles in a modern quantum field theory description.

The normal force is due to the Pauli exclusion principle almost exclusively. 

 This is because electrons have the property that two electrons cannot be in the same quantum state. Two electrons can't be at exactly the same point.

But you might be thinking, "two-point particles in three dimensions can't ever be at the same point, it's infinitely improbable!" In quantum mechanics, the particles are spread out in a wavefunction, and the condition that they can't be at the same point means that wherever their spread-out-ness overlaps, the wavefunction is zero. The wavefunction is in 6 dimensions for 2 particles, so it is hard to visualize, but the zeros appear on the diagonal part, where the two positions for the particle coincide.

When you bring two objects to touch, the electron wavefunctions are squeezed together, and the average scale of variation increases slightly, because of the exclusion. The rate of change of the wavefunction is the momentum of the electron, and as you push them closer, it costs energy. This is the source of the normal force. It would not exist if electrons were elementary bosons.

Motivational thought

JUST BE COMMITTED TO WHAT U R DOING AND,
" DON'T FEAR FAILURE BUT BE TERRIFIED OF REGRETTS "
                          

Leopard at IIT Bombay

With several instances of animal spotting at the Indian Institute of Technology Bombay (IIT-B), it seems to have become a common occurrence at the Powai campus. Days after the video of a cow taking a stroll inside one of the institute's classrooms went viral, a video of a leopard roaming inside the campus has hit the social media.

Precaution:- Speaking on condition of anonymity, the institute spokesperson said, "Somebody has shot a video of the leopard but the location cannot be confirmed. It could be the campus. But spotting leopards inside the campus is a regular occurrence. We have informed the forest department about it. However, we issue general guidelines to students, staff and others on campus throughout the year to remain alert and take precautionary measures as and when required. They should go out at night only in groups."

Regular instances:-
According to students, spotting of leopards inside the campus was a usual scenario. One of them said, "Leopards are usually spotted near the hilly area. If the situation gets serious, the authorities issue a warning apart from their regular directives." Another student said, "Instances of animals entering classrooms and hostels increases during the rainy season as they drift into the campus in search of shade."

Use of ROTOR present on the Tail of helicopter(An awesome example of Angular Momentum)

Helicopter p.c.:-Google 

Helicopters have a tail rotor or a second main rotor spinning in opposite direction(e.g. Chinook Helicopter) because otherwise along with the primary rotor the body would counterrotate with the primary rotor to give a

 total angular momentum = 0. 

This is the reason when u take a toy helicopter with no tail rotor then u will observe that when u fly that helicopter up then along with its flight the body of the helicopter also counters rotate w.r.t. the primary rotor to nullify the total angular momentum. But the presence of a tail rotor, the thrust produced by tail rotor compensates for the rotation of the body in the opposite direction(torque). As shown in the above diagram