you are provided with a hollow iron ball A of volume 15cm3 and mass 12 g and a solid iron ball B of mass 12g both are placed on the surface of water contained in a large tub find ther upthrust on each ball which ball will sink give reason for your answer

 

Asked by sherilstanly | 13th Aug, 2018, 07:46: PM

Expert Answer:

Upthrust = ( V×ρw  - m )×g  ...............(1)
where V is displaced volume of water, ρw is water density, m is mass of solid and g is acceleration due to gravity
 
if we substitute vales for hollow ball-A, we get,  (15×10-6 ×1000 - 12×10-3)×9.8 = 3×10-3 ×9.8 = 29.4×10-3 N 
 
volume of solid ball-B = 12×10-3 / 7800  = 1.54 × 10-6 m3
 
Hence upthrust for ball-B = (1.54×10-6× 1000 - 12×10-3 )×9.8 = -10.46×10-3 × 9.8 = -103 ×10-3 N
 
since ball-B is giving negative upthrust, ball-B will sink.

Answered by Thiyagarajan K | 14th Aug, 2018, 12:32: PM

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