can u tell me that why a body sink and why a body float

Asked by RAJNI | 10th Sep, 2014, 07:49: PM

Expert Answer:

When an object is put in a liquid , then two forces acts on it:

1. Weight of the object acting downwards (this pulls the object downwards).
2. The upthrust or the buoyant force acting upwards( this pushes the object upwards)
These two forces acts in the opposite direction.

So when the upthrust(buoyant force) exerted by the liquid is less than the weight of the object, the object will sink in the liquid.And when the upthrust exerted by the liquid is equal to the weight of the object, then the object will float in the liquid. When the upthrust exerted by the liquid is more than the weight of the object, the object will rise in the liquid and then float.
According to Archimedes' principle when an object is wholly or partially immersed in a liquid, it experiences a buoyant force or upthrust which is equal to the weight of liquid displaced by the object.So we can say that : An object will float in a liquid if the weight of the object is equal to the weight of the liquid displaced by it. Thus we observe that a rubber ball placed in water floats but a stone put in the same water sinks to the bottom.
Also an object will float in a liquid if its density is less than or equal to that of the liquid. eg: density of cork, wood, ice etc is less than water and they floats in water.
An object will sink in a liquid if its density is more than that of the liquid. eg :iron, glass and steel etc has density greater than water and hence they sinks in water.

Answered by Jyothi Nair | 11th Sep, 2014, 09:00: AM