The figure shows a table where some cutlery is placed on top of a table cloth. When the table cloth is pulled quickly, it is possible that the cutlery lands directly on the same spot on the table and does not get carried away with the cloth. Which of the following serves as a reasonable explanation?
Correct answer: B. The instant nature of the movement coupled with the inertia of the cutlery prevents any movement of the cutlery
- A. The rapid pulling of the table cloth causes the plates and cloth to be charged. The repulsion of like charges then causes a levitation force to lift up the cutlery subtly
- B. The instant nature of the movement coupled with the inertia of the cutlery prevents any movement of the cutlery
- C. The cloth is slippery and offers no friction hence can be slipped out
- D. The cutlery is held permanently in the same position by gravitational force
Explanation
If the tablecloth is pulled slowly, friction (rubbing) between the cutlery and the tablecloth will cause the tablecloth to pull the cutlery with it (Hence, options C and D can both be rejected). But, if the tablecloth is pulled quickly, the cutlery does not move. Inertia keeps it in place because friction is not as strong when you pull fast. The trick works no matter how heavy an object is since friction is weaker for lighter objects. Provided you pull quickly enough, this trick can even be done with glasses or plates.
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