Question

Match the following:

Column A Column B
(i) The mean distance between (a) unit
the sun and the earth is
(ii) The unit of a solid angle is (b) mass
(iii) A beam balance measures (c) 7
(iv) The standard quantity is (d) one astronomical unit
called
(v) The total number of basic (e) steradian
units in SI is
[5 marks]

Answer 1

The Astronomical unit (AU) is a measure of length which is the mean of the distance between the Earth and the Sun. The mean distance is found out by averaging the distance of the position where Earth is the farthest to the Sun and the position where the Earth is the nearest to the Sun. [1 mark]

Solid angle is a three-dimensional analogue of an angle, such as that subtended by a cone or formed by planes meeting at a point. It is measured in steradian. [1 mark]

The beam balance is a device used for the determination of the mass of a body. It is used for high precision measurements like masses up to 250 grams. It consists of a pair of scale pans one at each end of a rigid beam. [1 mark]

We know that measurement is the comparison of an unknown quantity with some known quantity. This known fixed quantity is called a unit. [1 mark]

The SI system has seven base units, and they are unit of length, unit of mass, unit of time, unit of electric current, unit of temperature, unit of amount of substance, unit of luminous intensity. These units pertain to the seven fundamental scientific quantities: metre, kilogram, second, ampere, kelvin, mole and candela respectively. [1 mark]

Therefore, the correct matchings are (i)-(d); (ii)-(e); (iii)-(b); (iv)-(a); (v)-(c);