Achild is holding a ball with a diameter of 5.70 cm and average density of 0.0835 g/cm3 under water. determine the force (in n) needed to hold it completely submerged.

0.488 N

Explanation:

Given , The ball has diameter (d)=5.70 cm = 0.0570 m

radius(r) = d/2 = 2.85 cm = 0.0285 m

Average density

There are two forces acting on the ball.. i.e. The buoyancy force and weight of the ball.

The force required to completely submerged under water= Buoyancy force - Weight of ball

buoyancy force = volume×density of water×g

[ density of water = 1000 kg/m3]

=0.532 N

mass of ball = average density×Volume

= 0.004529 kg

Weight of ball = mg = 0.004529×9.81 =0.044 N

Required force = 0.532 - 0.044 = 0.488 N.

the answer is b ) square root of 5