Question

Why we cannot open or close a door by applying force at the hinges?

Answer 1

For opening a door, we need to create a moment of force on the door about the fixed hinges.
Moment of Force = Force * Distance from hinges
Now, using the above formula,
If we apply force at hinges, then the distance from the hinges will be zero and hence the moment of force will be zero and we will not be able to even move the door.
The greater the distance from hinges, the easier it will be for opening the door.

Answer 2

HLO MATE HERE U GO

TORQUE = FORCE × Lever arm of the force .

when the force is applied at hinges , lever arm of the force will be zero.

so there will be no torque and hence we cannot open or close the door.