Category : JEE Main & Advanced
If a body of weight W is placed on the liquid surface, whose surface tension is T. If F is the minimum force required to pull it away from the water then value of F for different bodies can be calculated by the following table.
Body | Figure | Force |
Needle (Length \[=l\]) |
\[F=2lTW\] | |
Hollow disc (Inner radius \[={{r}_{1}}\] Outer radius \[={{r}_{2}}\]) |
\[F=2\pi ({{r}_{1}}+{{r}_{2}})T+W\] | |
Thin ring (Radius \[=r\]) | \[F=2\pi (r+r)T+W\] \[F=4\pi rT+W\] | |
Circular plate or disc (Radius \[=r\]) |
\[F=2\pi rT+W\] | |
Square frame (Side = l ) |
F = 8l T + W | |
Square plate | F = 4l T + W |
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