2.1.2 Estimating Physical Quantities

Question 1

What is a reasonable estimation?

Answer 1

One with the correct order of magnitude (to 1sf), units and on that can be mentally performed if required.

Question 2

Why estimate? Produce an example.

Answer 2

If the estimated quantity cannot be measured directly, it should be done by means of comparison - eg: the width of a note as the same as the width of a piece of paper.

Question 3

How do you ensure that an estimation is to the correct order of magnitude?

Answer 3

Round your value to the nearest power of 10; thus it should be accurate to the correct order of magnitude.

Question 4

Name three methods of estimation and produce an example for each.

Answer 4

1. By method of ratio:
   How much larger is the mass of DNA compared to a proton? These values will be given in some form of standard form, and so do the ratios of this standard form power. 10^-18:10^-27 would mean the RHS is 10^9 times heavier.
2. By method of comparison:
   use the thickness of a £10 note as the thickness of a piece of paper, because they are comparable and ne cannot be measured.
3. By method of assumption:
   Assuming an apple to be spherical.