A table tennis ball has an average density of #0.084##g##/##cm^3# and a diameter of #3.8# #cm#. How large a force can just submerge the ball in water?

1 Answer
P dilip_k
Oct 20, 2016

Given
#d->"Diameter of a tenis ball"=3.8cm #

#rho->"Density of the tenis ball"=0.084gcm^-3#

#d_w->"Density of water"=1gcm^-3#

#"Volume of the ball",v=4/3pid^3/8#
#=1/6pixx(3.8)^3cm^3=28.73cm^3#

#w->"weight of the ball"=vxxrhoxxg#

when the ball is submerged the buoyant force acting on the ball wil be equal to the weight of displaced water.

So the bouyant force

#F_b=vxxdwxxg#

So the net downward force to be appliied on the ball to just submerge it will be

#F_"net"=F_b-w=vd_wg-vrhog=vg(d_w-rho)#

#=28.73xx980xx(1-0.084)"dyne"=25790.3"dyne"#

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