Question
Spring fitted doors close by themselves when released. You want to keep the door open for a long time, say for an hour. If you put a half kg stone in front of the open door, it does not help. The stone slides with the door and the door gets closed. However, if you sandwich a 20 gm piece of wood in the small gap between the door and the floor, the door stays open. Explain why a much lighter piece of wood is able to keep the door open while the heavy stone fails. Assume coefficient of friction between stone and ground and wood and ground are the same.
Answer: Option C
:
C
In this case, the door will apply a downward force on the wooden piece which will increase the normal force that the ground applies on the wooden piece. ∴ Limiting value of friction will increase.
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:
C
In this case, the door will apply a downward force on the wooden piece which will increase the normal force that the ground applies on the wooden piece. ∴ Limiting value of friction will increase.
Was this answer helpful ?
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