Q. A $700\, g$ solid cube having an edge of length $10\, cm$ floats in water. The volume of cube outside water is:
Delhi UMET/DPMTDelhi UMET/DPMT 2005
Solution:
When a solid body is immersed in a liquid, then there is some apparent loss in its weight.
Two forces act on the cube:
(i) weight (mg) of body (downwards)
(ii) upthrust (U) of liquid (upwards).
For floatation $U=m g$ Let $V$ be volume of cube inside liquid,
then $V \times d \times g=m g V \times 1000 \times 10$
$=0.7 \times 10$
$\Rightarrow V=\frac{7}{10.000} m^{3}=700\, cm ^{3}$
Total volume of cube $=(10\, cm )^{3}=100\, cm ^{3}$
Volume outside water $=1000-700=300\, cm ^{3}$
