Question

A 2.5-liter object (mass: 2 kg) is released from rest at a depth of 20 m below the surface of the ocean.

a) After it's released from rest, will the object rise to the surface or sink to the ocean floor? Explain.

b) Determine the object's acceleration after it's released.

c) Determine the speed of the object 3.5 seconds after it's released.

d) How far has the object traveled in that 3.5 seconds?

Answer 1

a) The object has a volume of 2.5 lit=2500 cc

So it will remove water of 2500cc =2500 gm=2.5 kg water.

Now the mass of the object is 2 kg, which is less than the mass of the removed mass, so by Archimedes' principle it will feel upward buoyant force. So the object will rise.

b) Now the upward force is the weight of the excess water it removed, i.e (2.5-2)kg=0.5 kg

So the upward force is,

We know that,

is the acceleration.

So the acceleration of the ofject is,

  

  

c) Now the speed after 3.5 sec is,

  

  

d) The object has travelled a distance,