HELP!!
i have a question!! from 1st video of 8.01 classical mechanics
In-fact 2 questions about measurement uncertainty
In 149.9 ± 0.1 cm .... does 0.1 cm actually means 0.0999999999999 and we round it off to 0.1 . i think what i am saying is right but still want to confirm from some expert
next question -
in case of 4 units - 3 units where least count is 1 units
answer will be 1 ± 2 units ? this method doesn't make sense in this case.

Question

HELP!!
i have a question!! from 1st video of 8.01 classical mechanics
In-fact 2 questions about measurement uncertainty
In 149.9 ± 0.1 cm .... does 0.1 cm actually means 0.0999999999999 and we round it off to 0.1 .﻿ i think what i am saying is right but still want to confirm from some expert
next question -
in case of 4 units - 3 units where least count is 1 units
answer will be 1 ± 2 units ? this method doesn't make sense in this case.

anonymous · Answer

1. It is not about rounding the uncertainty off to 1 mm. If the smallest graduation on your ruler is 1 mm, you cannot precisely measure anything smaller than 1 mm. You could only estimate for example that it's ca. 149.95 cm (1499.5 mm) long.
2. The uncertainty cannot be bigger than the length itself. In this case you need to use an instrument which is more precise.