3 The atmospheric pressure on a particular

day was measured as 750 mmHg.

Express this in nm-2? (Assume densityof

mercury is 136ookgm3 and g = 10Nkg-1'?

102000N/m2

This is the same as 102KN/m2 (where K = 10^3):

Explanation:

The expression 750 mmHg means 750 height the atmospheric pressure will cause mercury to be suspended due to gravity.

If we brought another fluid under investigation under the influence of the atmospheric pressure the height would be different)

Note that 750 mmHg would be the same as 750/1000 m Hg (when we convert the mm to m)

0.75mHg

Now to get the pressure in N/m2.

We multiply the height of mercury by the density by the acceleration due to gravity.

This is expressed mathematically thus;

H*d * g; let d - denote density

Hence we have;

H*d * g = 0.75 * 13600 * 10 = 102000N/m2;

Now let's look at the flip. side assuming you don't know the formula for what you require you could use the idea of Unit derivation;

The unit of interest is N/m2

The unit of height is m

The unit of density is kg/m3

The unit of g is Nkg-1

We would observe if we multiply

m * N/Kg * Kg/m3

We would have (m * N * Kg) / (kg*m3)

Kg cancels out, m cancels out one m from me remaining m2.

Hence our unit becomes N/m2

Note : the unit for density is wrongly expressed remember density is Mass / volume and their units are respectively kg/m3