In the coin and card experiment to prove inertia of rest, we see that when the card is flicked suddenly, the coin is left behind. But when the card is pushed slowly, the coin moves along with it. Why does not inertia of rest act on the coin then? If it is friction, then why does it not act on the coin when the card is flicked suddenly?
 

Asked by bjayanta | 1st Aug, 2015, 03:56: PM

Expert Answer:

When the card is pushed slowly, friction acts on the coin due to contact.
 
However, when the card is flicked suddenly, the force is much greater to overcome the frictional force. The coin gets a push vertically and for a moment it is not in contact with the card.
 
Due to this, no friction acts on it for a short moment and the coin remains where it was.

Answered by Romal Bhansali | 2nd Aug, 2015, 12:20: PM