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Physics – Bungee Jumping Problem

A 55kg woman bungee jumps from a bridge and reaches a maximum velocity of 24.2m/s. The bridge is 60m above the water. When the woman is at the bottom of her trajectory, she is 9 m above the water.
What is the spring constant of the bungee cord?

 

bungee

Asked Mina

Buoyancy

A pound coin floating in mercury (Photo credit: Wikipedia)

I read in one of my chapters that when a body is immersed in a container of water (kept on a weighing machine which  reads ‘W’ at first )the apparent weight lost by the body is equal to the buoyant force, and thus the reading ‘W’ increases.

Then I came across a question like this –

A beaker containing water kept on a weighing machine weighs W. A body of weight  ‘w’ is dropped in it. It is floating & experiencing a buoyant force B, then the reading on machine is –

(a)w+W
(b)W+B
(C)W+w-B
(d)W

please give me the answer and explanation
the book says answer is (a)
but I think it is (c)

(Anwesha posted this questions)

The answer is A.

The total force acting downwards is W+w and the weighing scale is providing an equal reaction. the normal reaction offered by the weighing scale is what we get as the reading.

therefore the reading on the weighing scale must be W+w

The buoyant force is acting on the object dropped and is not contributing to the normal reaction offered by the weighing scale.

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