Answer :
The friction force acts as a contact force between the hands and doorknob to avoid slipping of hands.
Doorknobs are generally the small handles that are mounted on doors to avail the opening and closing of doors. These handles provide the turning moment to the door, which is given as,
[tex]T=F \times r[/tex]
Here, F is the contact force applied force between the knob and hands and r is the radial distance between the handle and door.
Now, the friction plays a vital role in turning the doorknob due to following reasons:
- It plays the role of contact force to provide greater magnitude of turning moment (T), which will be helpful for smooth turning.
- It will avoid the slipping of hands and therefore a strong grip is formed between the hands and doorknob.
Thus, we can conclude that the friction force acts as a contact force between the hands and doorknob to avoid slipping of hands.
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