Complete Fig 1.1 to show each quantity and its unit.

Question 15

Complete Fig 1.1 to show each quantity and its unit. [4]

            Quantity                                  Unit

            speed                                       m s^-1

            density                       

                                                            s^-1

            electric field strength             

                                                            kg m s^-1

Reference: Past Exam Paper – June 2003 Paper 2 Q1

Solution:

Quantity                                  Unit

            speed                                       m s^-1

            density                                    kg m^-3

            frequency                               s^-1

            electric field strength              N C^-1 or V m^-1 or kg m s^-2 C^-1

            momentum or impulse          kg m s^-1

{The unit of density is kg m^-3 (= mass / volume).

A unit of s^-1 means that the quantity is ‘something divided by time’. The numerator should not have any unit. This could be frequency (= 1 / period) or count rate or activity or decay constant.

The question has NOT asked for the SI BASE unit. So, the unit of electric field strength can be given as N C^-1 (= force / charge) or V m^-1 (= p.d. / distance) or in SI base units, kg m² C^-1. However, there was no need to convert into SI base unit as this was not specified in the question.

In the unit kg m s^-1, kg is the unit of mass and m s^-1 is the unit of velocity. The quantity represented by ‘mass × velocity’ is momentum (or impulse).}