Uncertainty

Question 1

Give 3 different ways we can reduce uncertainty.

Answer 1

• Increase resolution of instrument/ ie. use instrument with smaller intervals.
• Take repeated readings
• Size of measurement taken.

Question 2

How do we work out the uncertainty of equipment where one judgement is made?

Answer 2

• ±1/2 of smallest interval

Question 3

How do we work out the uncertainty of equipment where two judgements are made (ie. 2 sources of uncertainty)?

Answer 3

• ±1/2 of smallest interval + - ±1/2 of smallest interval

Question 4

Reading: 1660mg, without any info on resolution of equipment, what would the uncertainty be?

Answer 4

Reading: 1660mg, without any info on resolution of equipment, what would the uncertainty be? - ±10
- Look at what place value the last significant digit is, in this case, its the tens.

Question 5

Reading: 1663mg, without any info on resolution of equipment, what would the uncertainty be?

Answer 5

-±1
- Look at what place value the last significant digit is, in this case its in the ones.

Question 6

If we have 10 leaves that need to be measured, what would lead to lowest uncertainty
1.) Measuring all the leaves together (gives length of 2.1mm)
2.) Measuring one leaf at a time and WHY?
Assume, that the uncertainty for measuring 1 leaf is ±0.cm.

Answer 6

• Measure length all leaves stacked on top of each other.
• 10 leaves together: 2.1 ±0.1
• 1 leaf: 0.21 ±0.01(reduces the uncertainty.)
• We can do this because percentage uncertainty in measuring 1 leaf = same as 10 leaves.

Question 7

How can uncertainty be calculated when we have repeated measurements?

Answer 7

• Calculate mean of repeated measurments.
• Range/ 2 = uncertainty of the repeated measurements.

Question 8

How do we calculate percentage uncertainty in repeated measurements?

Answer 8

uncertainty/ mean value x 100.