Exercise 1.4

Transcript

Exercise 1.4 Explain this statement clearly : “To call a dimensional quantity ‘large’ or ‘small’ is meaningless without specifying a standard for comparison”. In view of this, reframe the following statements wherever necessary : (a) atoms are very small objects (b) a jet plane moves with great speed (c) the mass of Jupiter is very large (d) the air inside this room contains a large number of molecules (e) a proton is much more massive than an electron (f) the speed of sound is much smaller than the speed of light. Words such as “large”, “small”, “fast” and “heavy” describe comparisons. A length of 1m, for example, is enormous compared with an atom but tiny compared with Earth. A dimensional quantity needs a reference quantity of the same kind. Part | Appropriate statement | Explanation (a) | Atoms are very small compared with ordinary objects such as a a football | A reference length is needed. (b) | A jet plane moves very fast compared with a train | A reference speed is needed. (c) | Jupiter has a very large mass compared with Earth. | A reference mass is needed. (d) | The air inside this room contains a larger number of molecules than one mole of air | Number of molecules is measured using moles. (e) | A proton is much more massive than an electron. | No reframing needed: This statement already provides a direct comparison between two physical quantities of the same type (mass) (f) | The speed of sound is much smaller than the speed of light. | No reframing needed: This statement already provides a direct comparison between two physical quantities of the same type (speed)