1.1 Physical Quantities and Measurement

1.1.1 Measurement

What are Physical Quantities?

• All measurable quantities are known as physical quantities.
• Examples of physical quantities include length, mass, time, and temperature.
• Physical quantities have both magnitude and unit.
• For instance, consider a person holding a bag of groceries with a mass of 5 kg.
  • In this example, 5 represents the magnitude of the mass, and kg represents the unit.
• Therefore, mass is an example of a physical quantity.

Measurement of length

• Length is a measurable physical quantity.
• A ruler is commonly used for measurements.
• Rulers cover lengths from millimeters to meters.
• Procedure:
  • Place the rod alongside the ruler.
  • Align one end of the rod with the ruler’s zero mark.
  • Determine the length by reading the position of the other end on the ruler’s scale.

Example:  Determine the length of rod placed on ruler as shown in figure.

Solution:

Initial measurement on ruler= 0cm 

End reading on ruler=  5.5cm

Length of rod = Final reading – initial reading=  5.5-0  =5.5cm

Example:  Four identical coins are placed on the ruler as shown in the figure. Determine the length of these coins.

Solution:

Initial measurement on ruler = 3cm

End reading on ruler = 15cm

Total length of five ball-bearings= 15-3 =12cm

❓ Exam Question 

0625/0972/22-Feb-Mar-2020-Q1

Q#:21 The diagram shows a rectangular metal sheet close to two rulers.

What is the area of the metal sheet?