Before the body is immersed,
The weight of water and jar = 700 grams.
A body of volume 100cc is immersed in water in the jar.
The weight of body = 100 grams.
Because 1cc = 19m.
(Since 51 unit for volume is 1m3 = 1000000 grams or 1000000 cc)
The weight of the water and jar after immersion = 700g + 100g = 800g or 0.8kg.

Pascal's Law states that the external pressure applied on an incompressible liquid is transmitted uniformly throughout the liquid.

The layer of the air around the earth upto certain height of about 300 km, is called as the atmosphere of the earth. Since air occupies space and has weight, it also exerts pressure. This pressure is called atmospheric pressure.

It is easier to swim in the sea water as compared to river water, Because sea water has dissolved salts in it, which increases the density of water and also increases its upthrust, so the body sink less and we can easily swim in it as compared to the river water, because river water is less dense than sea water.

Helium in the balloon is lighter than the air around it, it receives an upward thrust known as buoyancy. Because helium weighs less than the amount of air it has displaced. So it floats.

Pressure exerted by a liquid at a point is determined by
i) depth (h)
ii) density of the liquid (p)
iii) acceleration due to gravity (g)

Wood piece of mass 100g floating in water, it will experience an upthrust due to water displaced by the immersed part of the of the wood.
For a floating body, upthrust will be equal to the weight of the body. Therefore the apparent weight of the body will be zero.
(ie. the weight of the body in air - upthrust)

Density of water = 1g cm^-3
Density in SI unit = ?
1g = 1000 kg/m³
1 cm³ = 1 x 10^-6m³
1 g / cm3 = \(= \frac{10^-3}{10^-6}\)= 1000 kg/m³
In SI unit density of water is 1000 kg/m³.

Relative density is a measure of how dense one thing is when compared to a reference, the reference is usually water.
With respect to water, the relative density of 13600 kg m^-3 of mercury is 13.6.
ie = \(\frac {13600}{1000}\) = 13.6 times dense as water. (where 1000kg m^-3 in the density of water).

Density of water (p) = 1000 km/m3
Volume of block (v) = 300 cm³ = 300 x 10^-6 m³
Gravitational force (g) = 10 ms^-2
Up thrust = pgv
= 1000 x 10 x 300 x 10^-6
= 3000000 x 10^-6 (10^-6 = 1000000)
\(\frac{3000000}{1000000}\)
Upthrust due to water = 3N