Question

A body of mass 2 kg is floating in water with half it's volume submerged .The force required to wholly submerge the body into water is

Answer 1

we know buoyant force =weight of water displaced
weight of body=2kg×9.8m/s^2
=19.6N= Weight of water displaced

so buoyant force=19.6N

Answer 2

The force required to wholly submerge the body into the water is 19.6 N

• We are given that the mass of the body, m = 2kg. Also, the body is floating in the water, with half its volume submerged
• Gravitational force is acting on the body, obviously, pulling it downwards. Yet, the body does not submerge into the water
• This is because of the buoyant force of water which acts in the opposite direction of gravity
• This buoyant force will be equal in magnitude (and opposite in direction) to the natural force acting on the body (the gravitational force) which pulls it downwards, which is equal to the weight of water that is displaced by the body
• Buoyant force = Weight of water displaced
  $F = m \times g$ [where $g = 9.8 \hspace{0.1cm} m/s^2$ is the acceleration due to gravity]
  $F = 2 \times 9.6$
  $F = 19.6 \hspace{0.1cm} N$
• Now, the force required to wholly submerge the body into water will be equal to the buoyant force that is acting on the body, which lets the body float
• That is, the force required to wholly submerge the body into the water is 19.6 N

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