Why is weight of the body is less in water than in air?

The weight of the body is less in water than in air because when body is immersed in water upthrust acts vertically upward which reduces the downward force on the body  but in air, the upthrust is negligible or equal to weight so weight is more. Hence , the weight is less in water. 

Air resistance and water resistance are kinds of friction. Solid things, like your chair, push up on you. Upwards forces from water or air are called upthrust.This force is called the upthrust. A piece of wood floating on water, and a helium balloon floating in the air, are both effects of upthrust. ... It states that: the upthrust is equal to the weight of the fluid displaced.Therefore, at sea level, air is 784 times less dense than water.Upthrust = apparent loss of weight of object = weight in air - weight in liquid.

If the upthrust is larger than the weight of the object, the object will rise. This happens when you jump into a swimming pool and then rise back up to the surface. Under the surface, the weight of water you displace - the upthrust - is more than your weight, so there is a resultant upwards force.A non-contact force is a force which acts on an object without coming physically in contact with it. The most familiar non-contact force is gravity, which confers weight. In contrast a contact force is a force applied to a body by another body that is in contact with it.

The upthrust on an object stays the same no matter how deep it goes (as long as it is completely submerged). This is because the upthrust depends only on the DIFFERENCE between the forces on the top and bottom of the object.The three types of buoyancy are positive buoyancy, negative buoyancy, and neutral buoyancy. Positive buoyancy is when the immersed object is lighter than the fluid displaced and this is the reason why the object floats.The effect of upthrust is that weight of the body immersed in a liquid appears to be less than its actual weight. There are two factors on which upthrust depends - Volume of the body and Density of the Liquid. Larger the volume of body submerged in liquid, greater is the upthrust.

Compressed air takes less volume, so has higher density. ... Determining its weight, and the volume of water it displaces, will determine whether it will float or sink. Note that if more air is added to the tank, it will get slightly heavier (and the volume will remain constant), and will therefore be less buoyant.