Thu March 03, 2011 By: Aakanksh Ravi

how can a man swim in water when his weight is greater than the upthrust ?explain the physics behind this

Expert Reply
Mon March 07, 2011
Dear student,
When we are swimming we feel that we are kind of supported by water. This is also due to the upward force exerted by water on our body. A man can lift a heavier stone more comfortably under water than he could in air. This is because the upward force of the water reduces his effort.

The average density of a live man is slightly greater than that of water, so he has to swim to save his life, when thrown into water.

The dead body of man floats on the surface of water because it becomes less dense than water owing to the disproportionate increase in volume to that of weight, due to imbibition of water and gases.

Also, the dead body is noticed with its head underneath the surface of water, because the density of his head is greater than that of water.

if weight is greater than the upthrust, he has to swim.
Hope this helps.
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